Trace in a hostile environment (snippet to use for printf debugging)

ghetto-trace.c

// (Ghetto trace) (Trace in an hostile environment)
#include <stdlib.h>
#define UU_TRACE_BEGIN
#define UU_TRACE_END
#if defined (_WIN32)
extern "C" {
    __declspec(dllimport) unsigned long __stdcall GetCurrentProcessId(void);
    void __stdcall OutputDebugStringA(_In_opt_ char const *outputString);
    __declspec(dllimport) int _snprintf( char* buffer, size_t buf_size, const char* format, ... );
}
#    pragma comment(lib, "Kernel32")
#    if defined(_MSC_VER)
#        undef UU_TRACE_BEGIN
#        undef UU_TRACE_END
#        define UU_TRACE_BEGIN __pragma(warning(push)) __pragma(warning(disable: 4996))
#        define UU_TRACE_END __pragma(warning(pop))
#    endif
#endif
#define UU_TRACE(...) { UU_TRACE_BEGIN                                                 \
    static int fpi; static char fp[4096];                 \
    if (!fpi) { uint32_t pid=GetCurrentProcessId(); fpi=sprintf(fp, "trace-%x.txt", pid) >= 0; } \
    if (fpi) { FILE*y=fopen(fp, "a"); if (y) { fprintf(y, __VA_ARGS__); fputs("\n",y); fclose(y); } } \
UU_TRACE_END }
#define UU_DEBUG(...) { UU_TRACE_BEGIN
    char buffer[4096];                                                  \
    _snprintf(buffer, sizeof buffer, __VA_ARGS__); \
    OutputDebugStringA(buffer); OutputDebugStringA("\n"); \
UU_TRACE_END }
// (Ghetto trace)

trace.c

// (Begin):
#include <inttypes.h>
#if defined(_WIN32)
static uint64_t win32_now_micros()
{
  LARGE_INTEGER large_integer;
  QueryPerformanceFrequency(&large_integer);
  uint64_t ticks_per_second = large_integer.QuadPart;
  QueryPerformanceCounter(&large_integer);
  return 1000*1000*large_integer.QuadPart/ticks_per_second;
}
#endif

static uint64_t now_micros()
{
  return win32_now_micros();
}

static FILE* trace_output = stdout;

static void trace(int indent, char const* cat, char const* pattern, ...)
{
  char buffer[4096];
  va_list pattern_args;
  va_start(pattern_args, pattern);
  int buffer_i = vsnprintf(buffer, sizeof buffer, pattern, pattern_args);
  va_end(pattern_args);
  if (buffer_i < 0) return;

  uint64_t time_ms = now_micros() / 1000;
  FILE *o = trace_output;
  fprintf(o, "%*s" "%" PRIu64 ":%s: %s\n", indent, "", time_ms, cat, buffer), fflush(o);
}
// (End):