It would be convenient if there was a way for C/C++ code that is being compiled as part of a CodeQL test to know that it's part of a CodeQL test. This could be done by defining some type of macro that is defined when compiling any test, i.e. __CODEQL_TEST__.

The reason this would be useful is that I could easily compile and run this code outside of a CodeQL test without making any code modifications. Currently I am doing something like this:

#ifndef REAL_COMPILATION

extern int stdin;
extern char* fgets(char*, int, int);
extern char* strchr(const char*, int);
char getchar();
int atoi(char*);
int printf(const char*, ...);
void* malloc(unsigned long);
void puts(const char*);

#else

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#endif

And then when I want to test my code outside of CodeQL I do gcc test.c -DREAL_COMPILATION=1. This works for me, but it would be more convenient if CodeQL itself defined some macro that I could check, instead of requiring me to specify this when I compile the code manually.