What affects the behavior of GCC in nix-shell?

Suppose we have the following C code file:

#include <stdio.h>

int main() {
  char str[] = "Hello, World!";

  return 0;

It can be successfully compiled by installing gcc locally. But in nix-shell, it will fail:

1.c: In function ‘main’:
1.c:5:10: error: format not a string literal and no format arguments [-Werror=format-security]
    5 |   printf(str);
      |          ^~~
cc1: some warnings being treated as errors

My local here refers to installation through configuration.nix or home-manager. The same as the default version in nix-shell, both are 10.3.0.

In order to avoid compilation failure in nix-shell, I will deliberately append the parameters in the NIX_CFLAGS_COMPILE variable, for example:

mkShell {
   # ......
   shellHook =''
     export NIX_CFLAGS_COMPILE="-Wno-format-security $NIX_CFLAGS_COMPILE"

Can anyone tell me why this is?

I found the reason in the “Hardening flags” section of the C - NixOS Wiki.

:grinning_face_with_smiling_eyes: :sweat_smile: