diff --git a/ostd/algorithm.hh b/ostd/algorithm.hh
index 1e3df0c..6bcf556 100644
--- a/ostd/algorithm.hh
+++ b/ostd/algorithm.hh
@@ -6,8 +6,7 @@
 #ifndef OSTD_ALGORITHM_HH
 #define OSTD_ALGORITHM_HH
 
-#include <math.h>
-
+#include <cmath>
 #include <utility>
 #include <functional>
 #include <type_traits>
@@ -148,10 +147,9 @@ namespace detail {
 
     template<typename R, typename C>
     inline void introsort(R range, C &compare) {
-        detail::introloop(
-            range, compare,
-            static_cast<range_size_t<R>>(2 * (log(range.size()) / log(2)))
-        );
+        detail::introloop(range, compare, static_cast<range_size_t<R>>(
+            2 * (std::log(range.size()) / std::log(2))
+        ));
     }
 } /* namespace detail */
 
diff --git a/ostd/concurrency.hh b/ostd/concurrency.hh
index 4d440d7..418861a 100644
--- a/ostd/concurrency.hh
+++ b/ostd/concurrency.hh
@@ -46,6 +46,7 @@
 #ifndef OSTD_CONCURRENCY_HH
 #define OSTD_CONCURRENCY_HH
 
+#include <cstddef>
 #include <vector>
 #include <list>
 #include <thread>
@@ -162,7 +163,7 @@ public:
 
     /** @brief Deallocates a stack allocated with allocate_stack().
      *
-     * @see allocate_stack(), reserve_stacks(size_t), get_stack_allocator()
+     * @see allocate_stack(), reserve_stacks(), get_stack_allocator()
      */
     virtual void deallocate_stack(stack_context &st) noexcept = 0;
 
@@ -174,7 +175,7 @@ public:
      *
      * @see allocate_stack(), deallocate_stack(), get_stack_allocator()
      */
-    virtual void reserve_stacks(size_t n) = 0;
+    virtual void reserve_stacks(std::size_t n) = 0;
 
     /** @brief Gets a stack allocator using the scheduler's stack allocation.
      *
@@ -355,7 +356,7 @@ struct basic_thread_scheduler: scheduler {
         }
     }
 
-    void reserve_stacks(size_t n) {
+    void reserve_stacks(std::size_t n) {
         if constexpr(!SA::is_thread_safe) {
             std::lock_guard<std::mutex> l{p_lock};
             p_stacks.reserve(n);
@@ -595,7 +596,7 @@ public:
         p_stacks.deallocate(st);
     }
 
-    void reserve_stacks(size_t n) {
+    void reserve_stacks(std::size_t n) {
         p_stacks.reserve(n);
     }
 
@@ -720,7 +721,7 @@ public:
      * @param[in] sa The provided stack allocator.
      */
     basic_coroutine_scheduler(
-        size_t thrs = std::thread::hardware_concurrency(), SA &&sa = SA{}
+        std::size_t thrs = std::thread::hardware_concurrency(), SA &&sa = SA{}
     ):
         p_threads(thrs), p_stacks(std::move(sa))
     {}
@@ -830,7 +831,7 @@ public:
         }
     }
 
-    void reserve_stacks(size_t n) {
+    void reserve_stacks(std::size_t n) {
         if constexpr(!SA::is_thread_safe) {
             std::lock_guard<std::mutex> l{p_lock};
             p_stacks.reserve(n);
@@ -862,13 +863,13 @@ private:
     }
 
     void init() {
-        size_t size = p_threads;
+        std::size_t size = p_threads;
         std::vector<std::thread> thrs;
         thrs.reserve(size);
-        for (size_t i = 0; i < size; ++i) {
+        for (std::size_t i = 0; i < size; ++i) {
             thrs.emplace_back([this]() { thread_run(); });
         }
-        for (size_t i = 0; i < size; ++i) {
+        for (std::size_t i = 0; i < size; ++i) {
             if (thrs[i].joinable()) {
                 thrs[i].join();
             }
@@ -951,7 +952,7 @@ private:
         }
     }
 
-    size_t p_threads;
+    std::size_t p_threads;
     std::condition_variable p_cond;
     std::mutex p_lock;
     SA p_stacks;
@@ -1019,7 +1020,7 @@ inline generator<T> make_generator(F &&func) {
     return detail::current_scheduler->make_generator<T>(std::forward<F>(func));
 }
 
-inline void reserve_stacks(size_t n) {
+inline void reserve_stacks(std::size_t n) {
     detail::current_scheduler->reserve_stacks(n);
 }
 
diff --git a/ostd/context_stack.hh b/ostd/context_stack.hh
index cfba4cd..859223b 100644
--- a/ostd/context_stack.hh
+++ b/ostd/context_stack.hh
@@ -18,6 +18,7 @@
 #ifndef OSTD_CONTEXT_STACK_HH
 #define OSTD_CONTEXT_STACK_HH
 
+#include <cstddef>
 #include <new>
 #include <algorithm>
 
@@ -48,7 +49,7 @@ namespace ostd {
  */
 struct stack_context {
     void *ptr = nullptr; ///< The stack pointer.
-    size_t size = 0; ///< The stack size.
+    std::size_t size = 0; ///< The stack size.
 #ifdef OSTD_USE_VALGRIND
     int valgrind_id = 0;
 #endif
@@ -75,7 +76,7 @@ struct OSTD_EXPORT stack_traits {
      * some other value too. Stack sizes are typically a multiple of page
      * size.
      */
-    static size_t page_size() noexcept;
+    static std::size_t page_size() noexcept;
 
     /** @brief Gets the minimum size a stack can have.
      *
@@ -85,7 +86,7 @@ struct OSTD_EXPORT stack_traits {
      *
      * @see maximum_size(), default_size()
      */
-    static size_t minimum_size() noexcept;
+    static std::size_t minimum_size() noexcept;
 
     /** @brief Gets the maximum size a stack can have.
      *
@@ -95,7 +96,7 @@ struct OSTD_EXPORT stack_traits {
      *
      * @see minimum_size(), default_size()
      */
-    static size_t maximum_size() noexcept;
+    static std::size_t maximum_size() noexcept;
 
     /** @brief Gets the default size for stacks.
      *
@@ -105,14 +106,14 @@ struct OSTD_EXPORT stack_traits {
      *
      * @see minimum_size(), maximum_size()
      */
-    static size_t default_size() noexcept;
+    static std::size_t default_size() noexcept;
 };
 
 namespace detail {
-    OSTD_EXPORT void *stack_alloc(size_t sz);
-    OSTD_EXPORT void stack_free(void *p, size_t sz) noexcept;
-    OSTD_EXPORT void stack_protect(void *p, size_t sz) noexcept;
-    OSTD_EXPORT size_t stack_main_size() noexcept;
+    OSTD_EXPORT void *stack_alloc(std::size_t sz);
+    OSTD_EXPORT void stack_free(void *p, std::size_t sz) noexcept;
+    OSTD_EXPORT void stack_protect(void *p, std::size_t sz) noexcept;
+    OSTD_EXPORT std::size_t stack_main_size() noexcept;
 }
 
 /** @brief A fixed size stack.
@@ -159,7 +160,7 @@ struct basic_fixedsize_stack {
      * The provided argument is the size used for the stacks. It defaults
      * to the default size used for the stacks according to the traits.
      */
-    basic_fixedsize_stack(size_t ss = Traits::default_size()) noexcept:
+    basic_fixedsize_stack(std::size_t ss = Traits::default_size()) noexcept:
         p_size(
             Traits::is_unbounded()
                 ? std::max(ss, Traits::minimum_size())
@@ -169,10 +170,10 @@ struct basic_fixedsize_stack {
 
     /** @brief Allocates a stack. */
     stack_context allocate() {
-        size_t ss = p_size;
+        std::size_t ss = p_size;
 
-        size_t pgs = Traits::page_size();
-        size_t asize = ss + pgs - 1 - (ss - 1) % pgs + (pgs * Protected);
+        std::size_t pgs = Traits::page_size();
+        std::size_t asize = ss + pgs - 1 - (ss - 1) % pgs + (pgs * Protected);
 
         void *p = detail::stack_alloc(asize);
         if constexpr(Protected) {
@@ -207,7 +208,7 @@ struct basic_fixedsize_stack {
      * stacks can be reserved ahead of time. This allocates only one stack
      * at a time, so this function does nothing.
      */
-    void reserve(size_t) {}
+    void reserve(std::size_t) {}
 
     /** @brief Gets the allocator for stack pool uses.
      *
@@ -220,7 +221,7 @@ struct basic_fixedsize_stack {
     }
 
 private:
-    size_t p_size;
+    std::size_t p_size;
 };
 
 /** @brief An unprotected fixed size stack using ostd::stack_traits. */
@@ -270,7 +271,7 @@ private:
 
 public:
     /** @brief The default number of stacks to store in each chunk. */
-    static constexpr size_t DEFAULT_CHUNK_SIZE = 32;
+    static constexpr std::size_t DEFAULT_CHUNK_SIZE = 32;
 
     /** @brief The traits type used for the stacks. */
     using traits_type = Traits;
@@ -303,11 +304,12 @@ public:
      * @param cs The number of stacks in each chunk.
      */
     basic_stack_pool(
-        size_t ss = Traits::default_size(), size_t cs = DEFAULT_CHUNK_SIZE
+        std::size_t ss = Traits::default_size(),
+        std::size_t cs = DEFAULT_CHUNK_SIZE
     ) {
         /* precalculate the sizes */
-        size_t pgs = Traits::page_size();
-        size_t asize = ss + pgs - 1 - (ss - 1) % pgs + (pgs * Protected);
+        std::size_t pgs = Traits::page_size();
+        std::size_t asize = ss + pgs - 1 - (ss - 1) % pgs + (pgs * Protected);
         p_stacksize = asize;
         p_chunksize = cs * asize;
     }
@@ -347,8 +349,8 @@ public:
 
     /** @brief Destroys the stack pool and all memory managed by it. */
     ~basic_stack_pool() {
-        size_t ss = p_stacksize;
-        size_t cs = p_chunksize;
+        std::size_t ss = p_stacksize;
+        std::size_t cs = p_chunksize;
         void *pc = p_chunk;
         while (pc) {
             void *p = pc;
@@ -363,12 +365,12 @@ public:
      * to contain. If it already contains that number or more, this function
      * does nothing. Otherwise it potentially reserves some extra chunks.
      */
-    void reserve(size_t n) {
-        size_t cap = p_capacity;
+    void reserve(std::size_t n) {
+        std::size_t cap = p_capacity;
         if (n <= cap) {
             return;
         }
-        size_t cnum = p_chunksize / p_stacksize;
+        std::size_t cnum = p_chunksize / p_stacksize;
         p_unused = alloc_chunks(p_unused, (n - cap + cnum - 1) / cnum);
     }
 
@@ -380,7 +382,7 @@ public:
      */
     stack_context allocate() {
         stack_node *nd = request();
-        size_t ss = p_stacksize - sizeof(stack_node);
+        std::size_t ss = p_stacksize - sizeof(stack_node);
         auto *p = reinterpret_cast<unsigned char *>(nd) - ss;
         if constexpr(Protected) {
             detail::stack_protect(p, Traits::page_size());
@@ -436,15 +438,15 @@ private:
         stack_node *next;
     };
 
-    stack_node *alloc_chunks(stack_node *un, size_t n) {
-        size_t ss = p_stacksize;
-        size_t cs = p_chunksize;
-        size_t cnum = cs / ss;
+    stack_node *alloc_chunks(stack_node *un, std::size_t n) {
+        std::size_t ss = p_stacksize;
+        std::size_t cs = p_chunksize;
+        std::size_t cnum = cs / ss;
 
-        for (size_t ci = 0; ci < n; ++ci) {
+        for (std::size_t ci = 0; ci < n; ++ci) {
             void *chunk = detail::stack_alloc(cs);
             stack_node *prevn = un;
-            for (size_t i = cnum; i >= 2; --i) {
+            for (std::size_t i = cnum; i >= 2; --i) {
                 auto nd = get_node(chunk, ss, i);
                 nd->next_chunk = nullptr;
                 nd->next = prevn;
@@ -473,7 +475,7 @@ private:
         return r;
     }
 
-    stack_node *get_node(void *chunk, size_t ssize, size_t n) {
+    stack_node *get_node(void *chunk, std::size_t ssize, std::size_t n) {
         return reinterpret_cast<stack_node *>(
             static_cast<unsigned char *>(chunk) + (ssize * n) - sizeof(stack_node)
         );
@@ -482,9 +484,9 @@ private:
     void *p_chunk = nullptr;
     stack_node *p_unused = nullptr;
 
-    size_t p_chunksize;
-    size_t p_stacksize;
-    size_t p_capacity = 0;
+    std::size_t p_chunksize;
+    std::size_t p_stacksize;
+    std::size_t p_capacity = 0;
 };
 
 /** @brief Swaps two stack pools. */
diff --git a/ostd/coroutine.hh b/ostd/coroutine.hh
index da3334c..5c5a896 100644
--- a/ostd/coroutine.hh
+++ b/ostd/coroutine.hh
@@ -20,6 +20,7 @@
 #ifndef OSTD_COROUTINE_HH
 #define OSTD_COROUTINE_HH
 
+#include <cstddef>
 #include <exception>
 #include <stdexcept>
 #include <typeinfo>
@@ -65,7 +66,7 @@ namespace detail {
 
     extern "C" OSTD_EXPORT
     fcontext_t OSTD_CDECL ostd_make_fcontext(
-        void *sp, size_t size, void (*fn)(transfer_t)
+        void *sp, std::size_t size, void (*fn)(transfer_t)
     );
 
     extern "C" OSTD_EXPORT
@@ -267,7 +268,7 @@ protected:
         p_stack = sa.allocate();
 
         void *sp = get_stack_ptr<SA>();
-        size_t asize = p_stack.size - (
+        std::size_t asize = p_stack.size - (
             static_cast<unsigned char *>(p_stack.ptr) -
             static_cast<unsigned char *>(sp)
         );
@@ -282,14 +283,14 @@ private:
     template<typename SA>
     void *get_stack_ptr() {
         /* 16 byte stack pointer alignment */
-        constexpr size_t salign = 16;
+        constexpr std::size_t salign = 16;
         /* makes enough space so that we can store the allocator at
          * stack pointer location (we'll need it for dealloc later)
          */
-        constexpr size_t sasize = sizeof(SA);
+        constexpr std::size_t sasize = sizeof(SA);
 
         void *sp = static_cast<unsigned char *>(p_stack.ptr) - sasize - salign;
-        size_t space = sasize + salign;
+        std::size_t space = sasize + salign;
         sp = std::align(salign, sasize, sp, space);
 
         return sp;
@@ -1203,8 +1204,8 @@ struct generator_range: input_range<generator_range<T>> {
     using range_category  = input_range_tag;
     using value_type      = T;
     using reference       = T &;
-    using size_type       = size_t;
-    using difference_type = ptrdiff_t;
+    using size_type       = std::size_t;
+    using difference_type = std::ptrdiff_t;
 
     /** Generator ranges are not default constructible. */
     generator_range() = delete;
diff --git a/ostd/environ.hh b/ostd/environ.hh
index 7fc9f43..1004e66 100644
--- a/ostd/environ.hh
+++ b/ostd/environ.hh
@@ -21,9 +21,8 @@
 #include "ostd/platform.hh"
 #include "ostd/internal/win32.hh"
 
-#include <stdlib.h>
-#include <string.h>
-
+#include <cstdlib>
+#include <cstring>
 #include <vector>
 #include <optional>
 
@@ -50,27 +49,11 @@ namespace ostd {
 inline std::optional<std::string> env_get(string_range name) {
     char buf[256];
     auto tbuf = to_temp_cstr(name, buf, sizeof(buf));
-#ifndef OSTD_PLATFORM_WIN32
-    char const *ret = getenv(tbuf.get());
+    char const *ret = std::getenv(tbuf.get());
     if (!ret) {
         return std::nullopt;
     }
     return std::string{ret};
-#else
-    std::vector<char> rbuf;
-    DWORD sz;
-    for (;;) {
-        sz = GetEnvironmentVariable(tbuf.get(), rbuf.data(), rbuf.capacity());
-        if (!sz) {
-            return std::nullopt;
-        }
-        if (sz < rbuf.capacity()) {
-            break;
-        }
-        rbuf.reserve(sz);
-    }
-    return std::string{rbuf.data(), sz};
-#endif
 }
 
 /** @brief Sets an environment variable.
diff --git a/ostd/event.hh b/ostd/event.hh
index 04a8799..5a9af07 100644
--- a/ostd/event.hh
+++ b/ostd/event.hh
@@ -6,6 +6,7 @@
 #ifndef OSTD_EVENT_HH
 #define OSTD_EVENT_HH
 
+#include <cstddef>
 #include <functional>
 #include <utility>
 
@@ -22,7 +23,7 @@ namespace detail {
             using func_t = std::function<void(C &, A...)>;
             auto *bufp = new unsigned char[sizeof(func_t) * p_nfuncs];
             func_t *nbuf = reinterpret_cast<func_t *>(bufp);
-            for (size_t i = 0; i < p_nfuncs; ++i)
+            for (std::size_t i = 0; i < p_nfuncs; ++i)
                 new (&nbuf[i]) func_t(ev.p_funcs[i]);
             p_funcs = nbuf;
         }
@@ -39,7 +40,7 @@ namespace detail {
             p_nfuncs = ev.p_nfuncs;
            auto *bufp = new unsigned char[sizeof(func_t) * p_nfuncs];
             func_t *nbuf = reinterpret_cast<func_t *>(bufp);
-            for (size_t i = 0; i < p_nfuncs; ++i) {
+            for (std::size_t i = 0; i < p_nfuncs; ++i) {
                 new (&nbuf[i]) func_t(ev.p_funcs[i]);
             }
             p_funcs = nbuf;
@@ -54,7 +55,7 @@ namespace detail {
         ~signal_base() { clear(); }
 
         void clear() {
-            for (size_t i = 0; i < p_nfuncs; ++i) {
+            for (std::size_t i = 0; i < p_nfuncs; ++i) {
                 using func = std::function<void(C &, A...)>;
                 p_funcs[i].~func();
             }
@@ -64,9 +65,9 @@ namespace detail {
         }
 
         template<typename F>
-        size_t connect(F &&func) {
+        std::size_t connect(F &&func) {
             using func_t = std::function<void(C &, A...)>;
-            for (size_t i = 0; i < p_nfuncs; ++i) {
+            for (std::size_t i = 0; i < p_nfuncs; ++i) {
                 if (!p_funcs[i]) {
                     p_funcs[i] = std::forward<F>(func);
                     return i;
@@ -74,7 +75,7 @@ namespace detail {
             }
             auto *bufp = new unsigned char[sizeof(func_t) * (p_nfuncs + 1)];
             func_t *nbuf = reinterpret_cast<func_t *>(bufp);
-            for (size_t i = 0; i < p_nfuncs; ++i) {
+            for (std::size_t i = 0; i < p_nfuncs; ++i) {
                 new (&nbuf[i]) func_t(std::move(p_funcs[i]));
                 p_funcs[i].~func_t();
             }
@@ -84,7 +85,7 @@ namespace detail {
             return p_nfuncs++;
         }
 
-        bool disconnect(size_t idx) {
+        bool disconnect(std::size_t idx) {
             if ((idx >= p_nfuncs) || !p_funcs[idx]) {
                 return false;
             }
@@ -97,7 +98,7 @@ namespace detail {
             if (!p_class) {
                 return;
             }
-            for (size_t i = 0; i < p_nfuncs; ++i) {
+            for (std::size_t i = 0; i < p_nfuncs; ++i) {
                 if (p_funcs[i]) {
                     p_funcs[i](*p_class, args...);
                 }
@@ -124,7 +125,7 @@ namespace detail {
     private:
         C *p_class;
         std::function<void(C &, A...)> *p_funcs;
-        size_t p_nfuncs;
+        std::size_t p_nfuncs;
     };
 } /* namespace detail */
 
@@ -151,9 +152,9 @@ public:
     void clear() { p_base.clear(); }
 
     template<typename F>
-    size_t connect(F &&func) { return p_base.connect(std::forward<F>(func)); }
+    std::size_t connect(F &&func) { return p_base.connect(std::forward<F>(func)); }
 
-    bool disconnect(size_t idx) { return p_base.disconnect(idx); }
+    bool disconnect(std::size_t idx) { return p_base.disconnect(idx); }
 
     template<typename ...Args>
     void emit(Args &&...args) { p_base.emit(std::forward<Args>(args)...); }
@@ -190,9 +191,9 @@ public:
     void clear() { p_base.clear(); }
 
     template<typename F>
-    size_t connect(F &&func) { return p_base.connect(std::forward<F>(func)); }
+    std::size_t connect(F &&func) { return p_base.connect(std::forward<F>(func)); }
 
-    bool disconnect(size_t idx) { return p_base.disconnect(idx); }
+    bool disconnect(std::size_t idx) { return p_base.disconnect(idx); }
 
     template<typename ...Args>
     void emit(Args &&...args) const { p_base.emit(std::forward<Args>(args)...); }
diff --git a/ostd/format.hh b/ostd/format.hh
index 83cb6cb..2f762bf 100644
--- a/ostd/format.hh
+++ b/ostd/format.hh
@@ -17,11 +17,8 @@
 #ifndef OSTD_FORMAT_HH
 #define OSTD_FORMAT_HH
 
-#include <stdio.h>
-#include <stdlib.h>
-#include <ctype.h>
-#include <cmath>
-
+#include <cstddef>
+#include <climits>
 #include <utility>
 #include <stdexcept>
 #include <locale>
@@ -111,8 +108,8 @@ namespace detail {
         return ret;
     }
 
-    inline size_t read_digits(string_range &fmt, char *buf) {
-        size_t ret = 0;
+    inline std::size_t read_digits(string_range &fmt, char *buf) {
+        std::size_t ret = 0;
         for (; !fmt.empty() && isdigit(fmt.front()); ++ret) {
             *buf++ = fmt.front();
             fmt.pop_front();
@@ -176,7 +173,7 @@ namespace detail {
 
     inline char const *escape_fmt_char(char v, char quote) {
         if ((v >= 0 && v < 0x20) || (v == quote)) {
-            return fmt_escapes[size_t(v)];
+            return fmt_escapes[std::size_t(v)];
         } else if (v == 0x7F) {
             return "\\x7F";
         }
@@ -185,7 +182,7 @@ namespace detail {
 
     /* retrieve width/precision */
     template<typename T, typename ...A>
-    inline int get_arg_param(size_t idx, T const &val, A const &...args) {
+    inline int get_arg_param(std::size_t idx, T const &val, A const &...args) {
         if (idx) {
             if constexpr(!sizeof...(A)) {
                 throw format_error{"not enough format args"};
@@ -414,8 +411,8 @@ namespace detail {
  *   allowed.
  * * Pointers are formatted then. If the `s` specifier is used, the pointer
  *   will be formatted as hex with the `0x` prefix. Otherwise it's converted
- *   to `size_t` and formatted with the specifier (might error depending on
- *   the specifier).
+ *   to `std::size_t` and formatted with the specifier (might error depending
+ *   on the specifier).
  * * Then integers are formatted. Using the `s` specifier is like using the
  *   `d` specifier.
  * * Floats follow. Using `s` is like using `g`.
@@ -623,7 +620,7 @@ struct format_spec {
      * @see set_width(), set_precision_arg();
      */
     template<typename ...A>
-    void set_width_arg(size_t idx, A const &...args) {
+    void set_width_arg(std::size_t idx, A const &...args) {
         p_width = detail::get_arg_param(idx, args...);
         p_has_width = p_arg_width = true;
     }
@@ -656,7 +653,7 @@ struct format_spec {
      * @see set_precision(), set_width_arg();
      */
     template<typename ...A>
-    void set_precision_arg(size_t idx, A const &...args) {
+    void set_precision_arg(std::size_t idx, A const &...args) {
         p_precision = detail::get_arg_param(idx, args...);
         p_has_precision = p_arg_precision = true;
     }
@@ -861,7 +858,7 @@ private:
     }
 
     bool read_spec() {
-        size_t ndig = detail::read_digits(p_fmt, p_buf);
+        std::size_t ndig = detail::read_digits(p_fmt, p_buf);
 
         bool havepos = false;
         p_index = 0;
@@ -877,11 +874,11 @@ private:
 
         /* parse flags */
         p_flags = p_gflags;
-        size_t skipd = 0;
+        std::size_t skipd = 0;
         if (havepos || !ndig) {
             p_flags |= detail::parse_fmt_flags(p_fmt, 0);
         } else {
-            for (size_t i = 0; i < ndig; ++i) {
+            for (std::size_t i = 0; i < ndig; ++i) {
                 if (p_buf[i] != '0') {
                     break;
                 }
@@ -944,7 +941,9 @@ private:
     }
 
     template<typename R>
-    void write_spaces(R &writer, size_t n, bool left, char c = ' ') const {
+    void write_spaces(
+        R &writer, std::size_t n, bool left, char c = ' '
+    ) const {
         if (left == bool(p_flags & FMT_FLAG_DASH)) {
             return;
         }
@@ -954,14 +953,14 @@ private:
     /* string base writer */
     template<typename R>
     void write_str(R &writer, bool escape, string_range val) const {
-        size_t n = val.size();
+        std::size_t n = val.size();
         if (has_precision()) {
-            n = std::min(n, size_t(precision()));
+            n = std::min(n, std::size_t(precision()));
         }
         write_spaces(writer, n, true);
         if (escape) {
             writer.put('"');
-            for (size_t i = 0; i < n; ++i) {
+            for (std::size_t i = 0; i < n; ++i) {
                 if (val.empty()) {
                     break;
                 }
@@ -989,7 +988,7 @@ private:
             if (esc) {
                 char buf[6];
                 buf[0] = '\'';
-                size_t elen = strlen(esc);
+                std::size_t elen = strlen(esc);
                 memcpy(buf + 1, esc, elen);
                 buf[elen + 1] = '\'';
                 write_val(writer, false, ostd::string_range{
@@ -1013,7 +1012,7 @@ private:
     void write_int(R &writer, bool ptr, bool neg, T val) const {
         /* binary representation is the biggest, assume grouping */
         char buf[sizeof(T) * CHAR_BIT * 2];
-        size_t n = 0;
+        std::size_t n = 0;
 
         char isp = spec();
         if (isp == 's') {
@@ -1053,11 +1052,11 @@ private:
             T vb = val % base;
             buf[n++] = (vb + "70"[vb < 10]) | cmask;
         }
-        size_t tn = n;
+        std::size_t tn = n;
         if (has_precision()) {
             int prec = precision();
-            if (size_t(prec) > tn) {
-                tn = size_t(prec);
+            if (std::size_t(prec) > tn) {
+                tn = std::size_t(prec);
             } else if (!prec && zval) {
                 tn = 0;
             }
@@ -1088,10 +1087,10 @@ private:
             write_spaces(writer, tn + (!!pfx * 2) + sign, true, '0');
         }
         if (tn) {
-            for (size_t i = 0; i < (tn - n); ++i) {
+            for (std::size_t i = 0; i < (tn - n); ++i) {
                 writer.put('0');
             }
-            for (size_t i = 0; i < n; ++i) {
+            for (std::size_t i = 0; i < n; ++i) {
                 writer.put(buf[n - i - 1]);
             }
         }
@@ -1209,7 +1208,7 @@ private:
          * char pointers are handled by the string case above
          */
         if constexpr(std::is_pointer_v<T>) {
-            write_int(writer, (spec() == 's'), false, size_t(val));
+            write_int(writer, (spec() == 's'), false, std::size_t(val));
             return;
         }
         /* integers */
@@ -1239,7 +1238,7 @@ private:
     /* actual writer */
     template<typename R, typename T, typename ...A>
     void write_arg(
-        R &writer, size_t idx, T const &val, A const &...args
+        R &writer, std::size_t idx, T const &val, A const &...args
     ) const {
         if (idx) {
             if constexpr(!sizeof...(A)) {
@@ -1302,7 +1301,7 @@ private:
     /* range writer */
     template<typename R, typename T, typename ...A>
     void write_range(
-        R &writer, size_t idx, bool expandval, string_range sep,
+        R &writer, std::size_t idx, bool expandval, string_range sep,
         T const &val, A const &...args
     ) const {
         if (idx) {
@@ -1323,7 +1322,7 @@ private:
         }
     }
 
-    template<size_t I, size_t N, typename R, typename T>
+    template<std::size_t I, std::size_t N, typename R, typename T>
     void write_tuple_val(
         R &writer, bool escape, string_range sep, T const &tup
     ) const {
@@ -1337,7 +1336,7 @@ private:
 
     template<typename R, typename T, typename ...A>
     void write_tuple(
-        R &writer, size_t idx, T const &val, A const &...args
+        R &writer, std::size_t idx, T const &val, A const &...args
     ) {
         if (idx) {
             if constexpr(!sizeof...(A)) {
@@ -1358,9 +1357,9 @@ private:
 
     template<typename R, typename ...A>
     void write_fmt(R &writer, A const &...args) {
-        size_t argidx = 1;
+        std::size_t argidx = 1;
         while (read_until_spec(writer)) {
-            size_t argpos = index();
+            std::size_t argpos = index();
             if (is_nested()) {
                 if (!argpos) {
                     argpos = argidx++;
@@ -1398,7 +1397,7 @@ private:
                     set_precision_arg(argpos - 2, args...);
                 }
                 if (arg_width()) {
-                    if (argpos <= (size_t(argprec) + 1)) {
+                    if (argpos <= (std::size_t(argprec) + 1)) {
                         throw format_error{"argument width not given"};
                     }
                     set_width_arg(argpos - 2 - argprec, args...);
@@ -1440,7 +1439,9 @@ private:
 
     template<typename R>
     struct fmt_num_put final: std::num_put<char, fmt_out<R>> {
-        fmt_num_put(size_t refs = 0): std::num_put<char, fmt_out<R>>(refs) {}
+        fmt_num_put(std::size_t refs = 0):
+            std::num_put<char, fmt_out<R>>(refs)
+        {}
         ~fmt_num_put() {}
     };
 
diff --git a/ostd/generic_condvar.hh b/ostd/generic_condvar.hh
index 5a5371e..5de40de 100644
--- a/ostd/generic_condvar.hh
+++ b/ostd/generic_condvar.hh
@@ -145,8 +145,8 @@ struct generic_condvar {
     }
 
 private:
-    static constexpr size_t cvars = sizeof(std::condition_variable);
-    static constexpr size_t icvars =
+    static constexpr auto cvars = sizeof(std::condition_variable);
+    static constexpr auto icvars =
         sizeof(detail::cond_impl<std::condition_variable>);
     std::aligned_storage_t<std::max(
         6 * sizeof(void *) + (icvars - cvars), icvars
diff --git a/ostd/io.hh b/ostd/io.hh
index 6b4b50e..068da1a 100644
--- a/ostd/io.hh
+++ b/ostd/io.hh
@@ -16,6 +16,7 @@
 #ifndef OSTD_IO_HH
 #define OSTD_IO_HH
 
+#include <cstddef>
 #include <cstdio>
 #include <cerrno>
 
@@ -203,7 +204,7 @@ struct OSTD_EXPORT file_stream: stream {
      *
      * @see write_bytes()
      */
-    size_t read_bytes(void *buf, size_t count);
+    std::size_t read_bytes(void *buf, std::size_t count);
 
     /** @brief Writes `count` bytes into the stream.
      *
@@ -211,7 +212,7 @@ struct OSTD_EXPORT file_stream: stream {
      *
      * @see read_bytes()
      */
-    void write_bytes(void const *buf, size_t count);
+    void write_bytes(void const *buf, std::size_t count);
 
     /** @brief Reads a single character from the stream.
      *
@@ -280,8 +281,8 @@ namespace detail {
     struct stdout_range: output_range<stdout_range> {
         using value_type      = char;
         using reference       = char &;
-        using size_type       = size_t;
-        using difference_type = ptrdiff_t;
+        using size_type       = std::size_t;
+        using difference_type = std::ptrdiff_t;
 
         stdout_range() {}
         void put(char c) {
diff --git a/ostd/platform.hh b/ostd/platform.hh
index 43b9862..2b1e463 100644
--- a/ostd/platform.hh
+++ b/ostd/platform.hh
@@ -23,7 +23,7 @@
 #ifndef OSTD_PLATFORM_HH
 #define OSTD_PLATFORM_HH
 
-#include <stdlib.h>
+#include <cstddef>
 #include <cstdint>
 
 #include <type_traits>
@@ -278,7 +278,10 @@ inline std::uint64_t endian_swap64(std::uint64_t x) noexcept {
 
 /* endian swap */
 
-template<typename T, size_t N = sizeof(T), bool IsNum = std::is_arithmetic_v<T>>
+template<
+    typename T, std::size_t N = sizeof(T),
+    bool IsNum = std::is_arithmetic_v<T>
+>
 struct endian_swap;
 
 template<typename T>
diff --git a/ostd/range.hh b/ostd/range.hh
index 6f407d9..7bc2817 100644
--- a/ostd/range.hh
+++ b/ostd/range.hh
@@ -6,9 +6,7 @@
 #ifndef OSTD_RANGE_HH
 #define OSTD_RANGE_HH
 
-#include <stddef.h>
-#include <string.h>
-
+#include <cstddef>
 #include <new>
 #include <tuple>
 #include <utility>
@@ -273,7 +271,7 @@ inline range_size_t<IR> range_pop_front_n(IR &range, range_size_t<IR> n) {
         range = range.slice(n, rs);
         return n;
     } else {
-        size_t r = 0;
+        range_size_t<IR> r = 0;
         while (n-- && !range.empty()) {
             range.pop_front();
             ++r;
@@ -292,7 +290,7 @@ inline range_size_t<IR> range_pop_back_n(IR &range, range_size_t<IR> n) {
         range = range.slice(0, rs - n);
         return n;
     } else {
-        size_t r = 0;
+        range_size_t<IR> r = 0;
         while (n-- && !range.empty()) {
             range.pop_back();
             ++r;
@@ -404,8 +402,8 @@ template<typename T>
 struct noop_output_range: output_range<noop_output_range<T>> {
     using value_type      = T;
     using reference       = T &;
-    using size_type       = size_t;
-    using difference_type = ptrdiff_t;
+    using size_type       = std::size_t;
+    using difference_type = std::ptrdiff_t;
 
     void put(T const &) {}
 };
@@ -694,8 +692,8 @@ struct number_range: input_range<number_range<T>> {
     using range_category  = forward_range_tag;
     using value_type      = T;
     using reference       = T;
-    using size_type       = size_t;
-    using difference_type = ptrdiff_t;
+    using size_type       = std::size_t;
+    using difference_type = std::ptrdiff_t;
 
     number_range() = delete;
     number_range(T a, T b, T step = T(1)):
@@ -882,7 +880,7 @@ public:
 };
 
 namespace detail {
-    template<size_t I, size_t N, typename T>
+    template<std::size_t I, std::size_t N, typename T>
     inline void join_range_pop(T &tup) {
         if constexpr(I != N) {
             if (!std::get<I>(tup).empty()) {
@@ -893,7 +891,7 @@ namespace detail {
         }
     }
 
-    template<size_t I, size_t N, typename T>
+    template<std::size_t I, std::size_t N, typename T>
     inline auto join_range_front(T &tup) {
         if constexpr(I != N) {
             if (!std::get<I>(tup).empty()) {
@@ -1051,8 +1049,8 @@ struct appender_range: output_range<appender_range<T>> {
     void clear() { p_data.clear(); }
     bool empty() const { return p_data.empty(); }
 
-    void reserve(typename T::size_type cap) { p_data.reserve(cap); }
-    void resize(typename T::size_type len) { p_data.resize(len); }
+    void reserve(size_type cap) { p_data.reserve(cap); }
+    void resize(size_type len) { p_data.resize(len); }
 
     size_type size() const { return p_data.size(); }
     size_type capacity() const { return p_data.capacity(); }
@@ -1245,7 +1243,7 @@ iterator_range<T const *> citer(std::initializer_list<T> init) noexcept {
     return iterator_range<T const *>(init.begin(), init.end());
 }
 
-template<typename T, size_t N>
+template<typename T, std::size_t N>
 struct ranged_traits<T[N]> {
     using range = iterator_range<T *>;
 
diff --git a/ostd/stream.hh b/ostd/stream.hh
index ea5053b..714a871 100644
--- a/ostd/stream.hh
+++ b/ostd/stream.hh
@@ -38,6 +38,7 @@
 #ifndef OSTD_STREAM_HH
 #define OSTD_STREAM_HH
 
+#include <cstddef>
 #include <cerrno>
 #include <cstdlib>
 #include <type_traits>
@@ -223,7 +224,7 @@ struct stream {
      *
      * @see write_bytes(), get_char(), get(), get_line()
      */
-    virtual size_t read_bytes(void *, size_t) {
+    virtual std::size_t read_bytes(void *, std::size_t) {
         throw stream_error{EINVAL, std::generic_category()};
     }
 
@@ -244,7 +245,7 @@ struct stream {
      *
      * @see read_bytes(), put_char(), put(), write()
      */
-    virtual void write_bytes(void const *, size_t) {
+    virtual void write_bytes(void const *, std::size_t) {
         throw stream_error{EINVAL, std::generic_category()};
     }
 
@@ -429,7 +430,7 @@ struct stream {
      * @throws ostd::stream_error on write failure.
      */
     template<typename T>
-    void put(T const *v, size_t count) {
+    void put(T const *v, std::size_t count) {
         write_bytes(v, count * sizeof(T));
     }
 
@@ -456,7 +457,7 @@ struct stream {
      * @throws ostd::stream_error on read failure.
      */
     template<typename T>
-    size_t get(T *v, size_t count) {
+    std::size_t get(T *v, std::size_t count) {
         /* if eof was reached, at least return how many values succeeded */
         return read_bytes(v, count * sizeof(T)) / sizeof(T);
     }
@@ -556,7 +557,7 @@ struct stream_range<T, true>: input_range<stream_range<T>> {
     using range_category  = input_range_tag;
     using value_type      = T;
     using reference       = T;
-    using size_type       = size_t;
+    using size_type       = std::size_t;
     using difference_type = stream_off_t;
 
     /** @brief Stream ranges are not default constructible. */
@@ -670,7 +671,7 @@ struct stream_line_range: input_range<stream_line_range<T, TC>> {
     using range_category  = input_range_tag;
     using value_type      = TC;
     using reference       = TC &;
-    using size_type       = size_t;
+    using size_type       = std::size_t;
     using difference_type = stream_off_t;
 
     /** @brief Stream line ranges are not default constructible. */
diff --git a/ostd/string.hh b/ostd/string.hh
index 3a7bab9..40efc8c 100644
--- a/ostd/string.hh
+++ b/ostd/string.hh
@@ -6,10 +6,8 @@
 #ifndef OSTD_STRING_HH
 #define OSTD_STRING_HH
 
-#include <stdio.h>
-#include <stddef.h>
-#include <ctype.h>
-
+#include <cstddef>
+#include <cctype>
 #include <string>
 #include <string_view>
 #include <type_traits>
@@ -27,8 +25,8 @@ struct basic_char_range: input_range<basic_char_range<T>> {
     using range_category  = contiguous_range_tag;
     using value_type      = T;
     using reference       = T &;
-    using size_type       = size_t;
-    using difference_type = ptrdiff_t;
+    using size_type       = std::size_t;
+    using difference_type = std::ptrdiff_t;
 
 private:
     struct nat {};
@@ -43,7 +41,7 @@ public:
         std::is_convertible_v<U, T *>, nat
     > = nat{}): p_beg(beg) {
         if constexpr(std::is_array_v<std::remove_reference_t<U>>) {
-            size_t N = std::extent_v<std::remove_reference_t<U>>;
+            std::size_t N = std::extent_v<std::remove_reference_t<U>>;
             p_end = beg + N - (beg[N - 1] == '\0');
         } else {
             p_end = beg + (beg ? TR::length(beg) : 0);
@@ -95,16 +93,16 @@ public:
 
     T &back() const { return *(p_end - 1); }
 
-    size_t size() const { return p_end - p_beg; }
+    size_type size() const { return p_end - p_beg; }
 
-    basic_char_range slice(size_t start, size_t end) const {
+    basic_char_range slice(size_type start, size_type end) const {
         return basic_char_range(p_beg + start, p_beg + end);
     }
-    basic_char_range slice(size_t start) const {
+    basic_char_range slice(size_type start) const {
         return slice(start, size());
     }
 
-    T &operator[](size_t i) const { return p_beg[i]; }
+    T &operator[](size_type i) const { return p_beg[i]; }
 
     void put(T v) {
         if (p_beg == p_end) {
@@ -118,7 +116,7 @@ public:
 
     /* non-range */
     int compare(basic_char_range<T const> s) const {
-        size_t s1 = size(), s2 = s.size();
+        size_type s1 = size(), s2 = s.size();
         int ret;
         if (!s1 || !s2) {
             goto diffsize;
@@ -131,9 +129,9 @@ diffsize:
     }
 
     int case_compare(basic_char_range<T const> s) const {
-        size_t s1 = size(), s2 = s.size();
-        for (size_t i = 0, ms = std::min(s1, s2); i < ms; ++i) {
-            int d = toupper(p_beg[i]) - toupper(s[i]);
+        size_type s1 = size(), s2 = s.size();
+        for (size_type i = 0, ms = std::min(s1, s2); i < ms; ++i) {
+            int d = std::toupper(p_beg[i]) - std::toupper(s[i]);
             if (d) {
                 return d;
             }
@@ -381,7 +379,7 @@ inline std::basic_string<std::remove_cv_t<range_value_t<R>>, TR, A> make_string(
 
 inline namespace literals {
 inline namespace string_literals {
-    inline string_range operator "" _sr(char const *str, size_t len) {
+    inline string_range operator "" _sr(char const *str, std::size_t len) {
         return string_range(str, str + len);
     }
 }
@@ -396,12 +394,15 @@ private:
 public:
     temp_c_string() = delete;
     temp_c_string(temp_c_string const &) = delete;
-    temp_c_string(temp_c_string &&s): p_buf(s.p_buf), p_allocated(s.p_allocated) {
+    temp_c_string(temp_c_string &&s):
+        p_buf(s.p_buf), p_allocated(s.p_allocated)
+    {
         s.p_buf = nullptr;
         s.p_allocated = false;
     }
-    temp_c_string(R input, std::remove_cv_t<range_value_t<R>> *sbuf, size_t bufsize)
-    : p_buf(nullptr), p_allocated(false) {
+    temp_c_string(
+        R input, std::remove_cv_t<range_value_t<R>> *sbuf, std::size_t bufsize
+    ): p_buf(nullptr), p_allocated(false) {
         if (input.empty()) {
             return;
         }
@@ -427,8 +428,12 @@ public:
         return *this;
     }
 
-    operator std::remove_cv_t<range_value_t<R>> const *() const { return p_buf; }
-    std::remove_cv_t<range_value_t<R>> const *get() const { return p_buf; }
+    operator std::remove_cv_t<range_value_t<R>> const *() const {
+        return p_buf;
+    }
+    std::remove_cv_t<range_value_t<R>> const *get() const {
+        return p_buf;
+    }
 
     void swap(temp_c_string &s) {
         using std::swap;
@@ -444,7 +449,7 @@ inline void swap(temp_c_string<R> &a, temp_c_string<R> &b) {
 
 template<typename R>
 inline temp_c_string<R> to_temp_cstr(
-    R input, std::remove_cv_t<range_value_t<R>> *buf, size_t bufsize
+    R input, std::remove_cv_t<range_value_t<R>> *buf, std::size_t bufsize
 ) {
     return temp_c_string<R>(input, buf, bufsize);
 }
@@ -455,7 +460,7 @@ namespace std {
 
 template<typename T, typename TR>
 struct hash<ostd::basic_char_range<T, TR>> {
-    size_t operator()(ostd::basic_char_range<T, TR> const &v) const {
+    std::size_t operator()(ostd::basic_char_range<T, TR> const &v) const {
         return hash<std::basic_string_view<std::remove_const_t<T>, TR>>{}(v);
     }
 };
diff --git a/ostd/thread_pool.hh b/ostd/thread_pool.hh
index ee3f3bd..666bc3d 100644
--- a/ostd/thread_pool.hh
+++ b/ostd/thread_pool.hh
@@ -15,6 +15,7 @@
 #ifndef OSTD_THREAD_POOL_HH
 #define OSTD_THREAD_POOL_HH
 
+#include <cstddef>
 #include <type_traits>
 #include <functional>
 #include <utility>
@@ -115,12 +116,12 @@ struct thread_pool {
      *
      * @param[in] size The number of threads to use.
      */
-    void start(size_t size = std::thread::hardware_concurrency()) {
+    void start(std::size_t size = std::thread::hardware_concurrency()) {
         p_running = true;
         auto tf = [this]() {
             thread_run();
         };
-        for (size_t i = 0; i < size; ++i) {
+        for (std::size_t i = 0; i < size; ++i) {
             p_thrs.push_back(std::thread{tf});
         }
     }
diff --git a/ostd/unordered_map.hh b/ostd/unordered_map.hh
index 57627f3..4ad601d 100644
--- a/ostd/unordered_map.hh
+++ b/ostd/unordered_map.hh
@@ -14,6 +14,7 @@
 #ifndef OSTD_UNORDERED_MAP_HH
 #define OSTD_UNORDERED_MAP_HH
 
+#include <cstddef>
 #include <unordered_map>
 #include <type_traits>
 
@@ -61,7 +62,7 @@ template<
     typename A = std::allocator<std::pair<K const, T>>, typename R
 >
 inline std::unordered_map<K, T, H, E, A> make_unordered_map(
-    R range, size_t bcount = 1, H const &hash = H{},
+    R range, std::size_t bcount = 1, H const &hash = H{},
     E const &kequal = E{}, A const &alloc = A{}
 ) {
     static_assert(
@@ -119,7 +120,7 @@ inline std::unordered_map<
     std::tuple_element_t<0, range_value_t<R>>,
     std::tuple_element_t<1, range_value_t<R>>, H, E, A
 > make_unordered_map(
-    R &&range, size_t bcount = 1, H const &hash = H{},
+    R &&range, std::size_t bcount = 1, H const &hash = H{},
     E const &kequal = E{}, A const &alloc = A{}
 ) {
     static_assert(
diff --git a/ostd/vecmath.hh b/ostd/vecmath.hh
index 6e67dec..1683c28 100644
--- a/ostd/vecmath.hh
+++ b/ostd/vecmath.hh
@@ -6,6 +6,8 @@
 #ifndef OSTD_VECMATH_HH
 #define OSTD_VECMATH_HH
 
+#include <cstddef>
+
 namespace ostd {
 
 template<typename T>
@@ -20,8 +22,8 @@ struct vec2 {
     vec2(T v): x(v), y(v) {}
     vec2(T x, T y): x(x), y(y) {}
 
-    T &operator[](size_t idx)       { return value[idx]; }
-    T  operator[](size_t idx) const { return value[idx]; }
+    T &operator[](std::size_t idx)       { return value[idx]; }
+    T  operator[](std::size_t idx) const { return value[idx]; }
 
     vec2 &add(T v) {
         x += v; y += v;
@@ -146,8 +148,8 @@ struct vec3 {
     vec3(T v): x(v), y(v), z(v) {}
     vec3(T x, T y, T z): x(x), y(y), z(z) {}
 
-    T &operator[](size_t idx)       { return value[idx]; }
-    T  operator[](size_t idx) const { return value[idx]; }
+    T &operator[](std::size_t idx)       { return value[idx]; }
+    T  operator[](std::size_t idx) const { return value[idx]; }
 
     vec3 &add(T v) {
         x += v; y += v; z += v;
@@ -272,8 +274,8 @@ struct vec4 {
     vec4(T v): x(v), y(v), z(v), w(v) {}
     vec4(T x, T y, T z, T w): x(x), y(y), z(z), w(w) {}
 
-    T &operator[](size_t idx)       { return value[idx]; }
-    T  operator[](size_t idx) const { return value[idx]; }
+    T &operator[](std::size_t idx)       { return value[idx]; }
+    T  operator[](std::size_t idx) const { return value[idx]; }
 
     vec4 &add(T v) {
         x += v; y += v; z += v; w += v;
diff --git a/src/context_stack.cc b/src/context_stack.cc
index 1f6f0d4..f128df1 100644
--- a/src/context_stack.cc
+++ b/src/context_stack.cc
@@ -3,6 +3,7 @@
  * This file is part of libostd. See COPYING.md for futher information.
  */
 
+#include <cstddef>
 #include <cstdlib>
 #include <new>
 #include <mutex>
@@ -35,7 +36,7 @@ namespace detail {
 #  endif
 #endif
 
-    OSTD_EXPORT void *stack_alloc(size_t sz) {
+    OSTD_EXPORT void *stack_alloc(std::size_t sz) {
 #if defined(OSTD_PLATFORM_WIN32)
         void *p = VirtualAlloc(0, sz, MEM_COMMIT, PAGE_READWRITE);
         if (!p) {
@@ -61,7 +62,7 @@ namespace detail {
 #endif
     }
 
-    OSTD_EXPORT void stack_free(void *p, size_t sz) noexcept {
+    OSTD_EXPORT void stack_free(void *p, std::size_t sz) noexcept {
 #if defined(OSTD_PLATFORM_WIN32)
         (void)sz;
         VirtualFree(p, 0, MEM_RELEASE);
@@ -74,18 +75,18 @@ namespace detail {
 #endif
     }
 
-    OSTD_EXPORT size_t stack_main_size() noexcept {
+    OSTD_EXPORT std::size_t stack_main_size() noexcept {
 #if defined(OSTD_PLATFORM_WIN32)
         /* 4 MiB for windows... */
         return 4 * 1024 * 1024;
 #else
         struct rlimit l;
         getrlimit(RLIMIT_STACK, &l);
-        return size_t(l.rlim_cur);
+        return std::size_t(l.rlim_cur);
 #endif
     }
 
-    OSTD_EXPORT void stack_protect(void *p, size_t sz) noexcept {
+    OSTD_EXPORT void stack_protect(void *p, std::size_t sz) noexcept {
 #if defined(OSTD_PLATFORM_WIN32)
         DWORD oo;
         VirtualProtect(p, sz, PAGE_READWRITE | PAGE_GUARD, &oo);
@@ -95,13 +96,13 @@ namespace detail {
     }
 
     /* used by stack traits */
-    inline void ctx_pagesize(size_t *s) noexcept {
+    inline void ctx_pagesize(std::size_t *s) noexcept {
 #if defined(OSTD_PLATFORM_WIN32)
         SYSTEM_INFO si;
         GetSystemInfo(&si);
-        *s = size_t(si.dwPageSize);
+        *s = std::size_t(si.dwPageSize);
 #elif defined(OSTD_PLATFORM_POSIX)
-        *s = size_t(sysconf(_SC_PAGESIZE));
+        *s = std::size_t(sysconf(_SC_PAGESIZE));
 #endif
     }
 
@@ -127,14 +128,14 @@ bool stack_traits::is_unbounded() noexcept {
 #endif
 }
 
-size_t stack_traits::page_size() noexcept {
-    static size_t size = 0;
+std::size_t stack_traits::page_size() noexcept {
+    static std::size_t size = 0;
     static std::once_flag fl;
     std::call_once(fl, detail::ctx_pagesize, &size);
     return size;
 }
 
-size_t stack_traits::minimum_size() noexcept {
+std::size_t stack_traits::minimum_size() noexcept {
 #if defined(OSTD_PLATFORM_WIN32)
     /* no func on windows, sane default of 8 KiB */
     return 8 * 1024;
@@ -144,7 +145,7 @@ size_t stack_traits::minimum_size() noexcept {
 #endif
 }
 
-size_t stack_traits::maximum_size() noexcept {
+std::size_t stack_traits::maximum_size() noexcept {
 #if defined(OSTD_PLATFORM_WIN32)
     /* value is technically undefined when is_unbounded() is
      * true, just default to 1 GiB so we actually return something
@@ -152,21 +153,21 @@ size_t stack_traits::maximum_size() noexcept {
     return 1024 * 1024 * 1024;
 #elif defined(OSTD_PLATFORM_POSIX)
     /* can be RLIM_INFINITY, but that's ok, see above */
-    return size_t(detail::ctx_rlimit().rlim_max);
+    return std::size_t(detail::ctx_rlimit().rlim_max);
 #endif
 }
 
-size_t stack_traits::default_size() noexcept {
+std::size_t stack_traits::default_size() noexcept {
 #if defined(OSTD_PLATFORM_WIN32)
     /* no func on windows either, default to 64 KiB */
     return 8 * 8 * 1024;
 #elif defined(OSTD_PLATFORM_POSIX)
     /* default to at least 64 KiB (see minimum_size comment) */
-    constexpr size_t r = std::max(8 * 8 * 1024, SIGSTKSZ);
+    constexpr std::size_t r = std::max(8 * 8 * 1024, SIGSTKSZ);
     if (is_unbounded()) {
         return r;
     }
-    size_t m = maximum_size();
+    std::size_t m = maximum_size();
     if (r > m) {
         return m;
     }
diff --git a/src/io.cc b/src/io.cc
index d03d6bf..5d2f66c 100644
--- a/src/io.cc
+++ b/src/io.cc
@@ -3,6 +3,7 @@
  * This file is part of libostd. See COPYING.md for futher information.
  */
 
+#include <cstddef>
 #include <cstdio>
 #include <cstdlib>
 #include <cerrno>
@@ -24,9 +25,9 @@ bool file_stream::open(string_range path, stream_mode mode) {
     buf[path.size()] = '\0';
     p_owned = false;
 #ifndef OSTD_PLATFORM_WIN32
-    p_f = std::fopen(buf, filemodes[size_t(mode)]);
+    p_f = std::fopen(buf, filemodes[std::size_t(mode)]);
 #else
-    if (fopen_s(&p_f, buf, filemodes[size_t(mode)]) != 0) {
+    if (fopen_s(&p_f, buf, filemodes[std::size_t(mode)]) != 0) {
         return false;
     }
 #endif
@@ -84,8 +85,8 @@ void file_stream::flush() {
     }
 }
 
-size_t file_stream::read_bytes(void *buf, size_t count) {
-    size_t readn = std::fread(buf, 1, count, p_f);
+std::size_t file_stream::read_bytes(void *buf, std::size_t count) {
+    std::size_t readn = std::fread(buf, 1, count, p_f);
     if (readn != count) {
         if (std::feof(p_f) != 0) {
             return readn;
@@ -95,7 +96,7 @@ size_t file_stream::read_bytes(void *buf, size_t count) {
     return readn;
 }
 
-void file_stream::write_bytes(void const *buf, size_t count) {
+void file_stream::write_bytes(void const *buf, std::size_t count) {
     if (std::fwrite(buf, 1, count, p_f) != count) {
         throw stream_error{EIO, std::generic_category()};
     }