replaced strerror() with thread-safe strerror_malloc()

src/string/cstr.c

@@ -1,3 +1,9 @@
+// Enable POSIX 2004 definitions.
+// Required to use strerror_r in ISO C.
+#ifndef _XOPEN_SOURCE 
+    #define _XOPEN_SOURCE 600
+#endif
+
 #include "tlibc/string/cstr.h"
 
 char* cstr_copy(cstr self){
@@ -70,3 +76,15 @@ char* vsprintf_malloc(cstr format, va_list args){
     }
     return buf;
 }
+
+#if defined(_WIN64) || defined(_WIN32)
+#define portable_strerror_s(BUF, BUFSIZE, ERRCODE) strerror_s(BUF, BUFSIZE, ERRCODE)
+#else
+#define portable_strerror_s(BUF, BUFSIZE, ERRCODE) strerror_r(ERRCODE, BUF, BUFSIZE)
+#endif
+char* strerror_malloc(int errcode){
+    const int buf_size = 256;
+    char* buf = malloc(buf_size);
+    portable_strerror_s(buf, buf_size, errcode);
+    return buf;
+}