Complicated functions that are they're too easy to misuse https://github.com/git/git/blob/master/banned.h

banned.h

//https://github.com/git/git/blob/master/banned.h
/*
There are a few standard C functions (like strcpy) which are
easy to misuse. E.g.:

char path[PATH_MAX];
strcpy(path, arg);

may overflow the "path" buffer. Sometimes there's an earlier
constraint on the size of "arg", but even in such a case
it's hard to verify that the code is correct. If the size
really is unbounded, you're better off using a dynamic
helper like strbuf:

struct strbuf path = STRBUF_INIT;
strbuf_addstr(path, arg);

or if it really is bounded, then use xsnprintf to show your
expectation (and get a run-time assertion):

char path[PATH_MAX];
xsnprintf(path, sizeof(path), "%s", arg);

which makes further auditing easier.

*/
#ifndef BANNED_H
#define BANNED_H

/*
 * This header lists functions that have been banned from our code base,
 * because they're too easy to misuse (and even if used correctly,
 * complicate audits). Including this header turns them into compile-time
 * errors.
 */

#define BANNED(func) sorry_##func##_is_a_banned_function

#undef strcpy
#define strcpy(x,y) BANNED(strcpy)
#undef strcat
#define strcat(x,y) BANNED(strcat)
#undef strncpy
#define strncpy(x,y,n) BANNED(strncpy)
#undef strncat
#define strncat(x,y,n) BANNED(strncat)

#undef sprintf
#undef vsprintf
#ifdef HAVE_VARIADIC_MACROS
#define sprintf(...) BANNED(sprintf)
#define vsprintf(...) BANNED(vsprintf)
#else
#define sprintf(buf,fmt,arg) BANNED(sprintf)
#define vsprintf(buf,fmt,arg) BANNED(sprintf)
#endif

#endif /* BANNED_H */