quick and dirty printf-logging with (compile time) 'multiple outputs'

ijsl.h

/* clang-format off */
/*
ijsl : IncredibleJunior Simple Log

quick and dirty printf-logging with (compile time) 'multiple outputs' implemented
as a stb-style header-file library[1] which means that in *ONE* source file declare
the implementation (see example) and the other source files should just include
this file.

example setup for Windows (declare OutputDebugStringA ourselves to avoid including windows.h)

#ifdef __cplusplus
extern "C" {
#endif
   __declspec(dllimport) void __stdcall OutputDebugStringA(const char *lpOutputString);
#ifdef __cplusplus
}
#endif
#include <stdio.h>
#define IJSL_log_impl(s) printf("%s", (s)), OutputDebugStringA((s))
#define IJSL_IMPLEMENTATION
#include "ijsl.h"

License:
   This software is dual-licensed to the public domain and under the following
   license: you are granted a perpetual, irrevocable license to copy, modify,
   publish, and distribute this file as you see fit.

References:
   [1] https://github.com/nothings/stb
*/

#ifndef IJSL_INCLUDED_H
#define IJSL_INCLUDED_H

#ifdef __cplusplus
extern "C" {
#endif

   extern void ijsl_log(const char *format, ...);

   #define IJSL_LOG(s, ...) ijsl_log(s "\n", ##__VA_ARGS__)

#ifdef __cplusplus
}
#endif

#endif

#ifdef IJSL_IMPLEMENTATION

#ifndef IJSL_TEMP_BUFFER_SIZE
   #define IJSL_TEMP_BUFFER_SIZE (32 * 1024)
#endif

#ifndef IJSL_snprintf
   #include <stdio.h>
   #include <stdarg.h>
   #define IJSL_snprintf(s, n, f, v) _vsnprintf_s((s), (n), _TRUNCATE, (f), (v))
#endif

#ifndef IJSL_log_impl
   #error IJSL_log_impl must be defined
   /* examples

   #define IJSL_log_impl(s) printf("%s", (s)), OutputDebugStringA((s))

   if file logging is also wanted:

   FILE *logfile;
   #define IJSL_log_impl(s) printf("%s", (s)), OutputDebugStringA((s)), (logfile ? fprintf(logfile, "%s", (s)) : 0)
   */
#endif

extern void ijsl_log(const char *msg_format, ...)
{
   char buffer[IJSL_TEMP_BUFFER_SIZE];
   va_list args;

   va_start(args, msg_format);

   if (0 > IJSL_snprintf(buffer, IJSL_TEMP_BUFFER_SIZE, msg_format, args))
      buffer[IJSL_TEMP_BUFFER_SIZE-1] = 0;

   IJSL_log_impl(buffer);

   va_end(args);
}

#endif

/* clang-format on */