Easily allocate strings with a printf-like function.

makestr.c

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <wchar.h>

char *makestr(char *format, ...) {
	va_list args;
	int size;
	char *result;
	
#if !defined(_WIN32)
	FILE *printf_dummy_file = fopen("/dev/null", "wb");
#else
	FILE *printf_dummy_file = fopen("NUL", "wb");
#endif
	
	va_start(args, format);
	
	size = vfprintf(printf_dummy_file, format, args);
	
	result = malloc(size + 1);
	if (result == NULL) return NULL;
	
	va_end(args);
	va_start(args, format);
	
	vsnprintf(result, size + 1, format, args);
	result[size] = '\0';
	
	fclose(printf_dummy_file);
	
	return result;
}

wchar_t *wmakestr(wchar_t *format, ...) {
	va_list args;
	int size;
	wchar_t *result;
	
#if !defined(_WIN32)
	FILE *printf_dummy_file = fopen("/dev/null", "wb");
#else
	FILE *printf_dummy_file = fopen("NUL", "wb");
#endif
	
	va_start(args, format);
	
	size = vfwprintf(printf_dummy_file, format, args) * sizeof(wchar_t);
	
	result = malloc(size + 2);
	if (result == NULL) return NULL;
	
	va_end(args);
	va_start(args, format);
	
	vswprintf(result, size + 2, format, args);
	result[size] = L'\0';
	
	fclose(printf_dummy_file);
	
	return result;
}

/*///////////////////////////////////
	
		Testing:
		
///////////////////////////////////*/

int main(void) {
	char *str = makestr("Hello, %s! %i -> %2.1f", "word", 69, 2.5000f);
	wchar_t *wstr = wmakestr(L"Hello, %ls! %i -> %2.1f", L"word", 69, 2.5000f);
	
	printf("%s\n", str);
	wprintf(L"%ls\n", wstr);
	
	free(str);
	free(wstr);
	return 0;	
}