La Fée Verte @Absinthe@qoto.org

Cute little trick for gcc or clang users: (run valgrind on it afterwards)

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

#ifdef __cplusplus
extern "C" {
#endif

void raii_char_free(char **);

#define raii_char_pointer char * __attribute__ ((__cleanup__(raii_char_free)))

#ifdef __cplusplus
}
#endif

void raii_char_free(char **p) {
free(*p);
}

int main (void) {
raii_char_pointer ptr = strdup("abcdefg");
printf("%s\n", ptr);
return 0;
}

use a Makefile early and often.
Learn how to use a Makefile... Well.

Write unit tests before code.
Write documentation before code.
Use autodocumenting code like Doxygen.

use https://godbolt.org/ to test code on multiple compilers without having to have them installed locally

If you are programming in C consider adding c++ guards around your file scope variables and prototypes, and use the c++ compiler. You will find additional errors and warnings the c compilers alone won't find. Also, compile with both gcc and clang and use as many others as well as static analysis tools as you can. cppcheck can be your friend. valgrind can be your best friend.

when developing use -Wall and
-Wextra with gcc and -Weverything with clang... as a minimum. Consider pedantic also.

do not use dynamically allocated arrays on the stack. Do so on the heap only

if you allocate memory, you need to free it. strdup() allocates memory.... damnit!

String functions such as *printf() str*cmp() and others are meant to take string pointers. Under no circumstances should you use a function call, that returns NULL to indicate an error (like getenv()), as a parameter.

Unless you are working with an 8 bit compiler 0, '\0', and NULL are not synonyms.

When a C compiler gives you a warning, there is no reason to ignore it. If your code base is full of warnings how can you ever tell which poorly written piece of code is causing your current problem?

IBM XLC C compiler on AIX will treat a NULL as though it were an empty string "". There is a special circle of hell reserved for people that code counting on that behavior.