fixed realloc behavior, added getenv and reentrant strtok variant

code/os/win/win_env.c

@@ -3,7 +3,33 @@
 
 #include "win.h"
 
-_Noreturn void _os_exit(int code)
-{
+char* getenv(const char *name) {
+    // The string pointed to shall not be modified by the program, but may be
+    // overwritten by a subsequent call to the getenv function
+    static size_t env_string_cap;
+    static char* env_string;
+
+    DWORD env_length = GetEnvironmentVariable(name, NULL, 0);
+    if (env_length == 0) {
+        return 0;
+    }
+
+    // Upscale the internal string
+    if (env_length > env_string_cap) {
+        char* newstr = realloc(env_string, env_length);
+        if (newstr == NULL) {
+            free(env_string);
+            return 0;
+        }
+
+        env_string = newstr;
+        env_string_cap = env_length;
+    }
+
+    GetEnvironmentVariable(name, env_string, env_length);
+    return env_string;
+}
+
+_Noreturn void _os_exit(int code) {
     ExitProcess(code);
 }

code/os/win/win_mem.c

@@ -39,7 +39,7 @@ void *aligned_alloc(size_t alignment, size_t size) {
     if(alignment > 8) {
         min_req_size += alignment;
     }
-    void *block_start = HeapAlloc(_heap, HEAP_ZERO_MEMORY, min_req_size);
+    void *block_start = HeapAlloc(_heap, 0, min_req_size);
     intptr_t block_start_i = (intptr_t)block_start;
     intptr_t aligned_block_start_i = align_forward(block_start_i, alignment);
     void *aligned_block_start = (void *)aligned_block_start_i;
@@ -69,7 +69,14 @@ void *malloc(size_t size) {
 }
 
 void *realloc(void *ptr, size_t size) {
-    void *buffer = HeapReAlloc(_heap, 0, ptr, size);
-    return buffer;
-}
+    if (ptr == NULL) {
+        if (size == 0) return NULL;
 
+        return HeapAlloc(_heap, 0, size);
+    } else if (size == 0) {
+        HeapFree(_heap, 0, ptr);
+        return NULL;
+    } else {
+        return HeapReAlloc(_heap, 0, ptr, size);
+    }
+}

code/stdlib/env.c

@@ -38,4 +38,3 @@ _Noreturn void _Exit(int status) {
     // doesn't run atexit routines
     _os_exit(status);
 }
-

code/string.c

@@ -179,27 +179,30 @@ char *strstr(const char *s1, const char *s2) {
 
 // TODO: there may be restrict-related UB
 char *strtok(char *restrict s1, const char *restrict s2) {
-    static char *restrict str;
-    if(s1 != NULL) str = s1;
-    if(str == NULL) return NULL;
+    static char *str;
+    return strtok_r(s1, s2, &str);
+}
 
-    size_t junk_len = strspn(str, s2);
-    char *tok_start = str+junk_len;
+char *strtok_r(char *restrict s1, const char *restrict s2, char **restrict ctx) {
+    if(s1 != NULL) *ctx = s1;
+    if(*ctx == NULL) return NULL;
+
+    size_t junk_len = strspn(*ctx, s2);
+    char *tok_start = *ctx + junk_len;
     if(*tok_start == 0) {
-        str = NULL;
+        *ctx = NULL;
         return NULL;
     }
 
-    size_t tok_len = strcspn(str, s2);
+    size_t tok_len = strcspn(*ctx, s2);
 
     char *tok_end = tok_start + tok_len;
     *tok_end = 0;
-    str = tok_end+1;
+    *ctx = tok_end+1;
 
     return tok_start;
 }
 
-
 char *strerror(int errnum) {
     switch(errnum) {
         case 0:      return "No errors";

inc/stdlib.h

@@ -68,7 +68,7 @@ int atexit(void (*func)(void));
 // int at_quick_exit(void (*func)(void));
 _Noreturn void exit(int status);
 _Noreturn void _Exit(int status);
-// char *getenv(const char *name);
+char *getenv(const char *name);
 // _Noreturn void quick_exit(int status);
 // int system(const char *string);
 // void *bsearch(const void *key, const void *base, size_t nmemb, size_t size, int (*compar)(const void *, const void *));

inc/string.h

@@ -47,6 +47,9 @@ void *memset(void *s, int c, size_t n);
 char *strerror(int errnum);
 size_t strlen(const char *s);
 
+// Linux extension: reentrant strtok
+char *strtok_r(char *restrict s1, const char *restrict s2, char **restrict ctx);
+
 #if __STDC_WANT_LIB_EXT1__ == 1
 errno_t memcpy_s(void *restrict s1, rsize_t s1max, const void *restrict s2, rsize_t n);
 errno_t memmove_s(void *s1, rsize_t s1max, const void *s2, rsize_t n);

test/test.c

@@ -23,6 +23,13 @@ void wack() {
 int main(int argc, char** argv) {
     atexit(wack);
 
+    char* path_env = getenv("PATH");
+    char *ctx, *path_token = strtok_r(path_env, ";", &ctx);
+    while(path_token) {
+        printf("%s\n", path_token);
+        path_token = strtok_r(NULL, ";", &ctx);
+    }
+
     test();
     char input[] = "A bird came down the walk";
     printf("Parsing the input string '%s'\n", input);