implicit declaration using -std=c99

Question

I\'m getting this warning: (-std=c99 -pedantic)

warning: implicit declaration of function ‘strndup’ [-Wimplicit-function-declaration]
         


        

Answer 1

My man strndup says

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       strdup():
           _SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE >= 500 ||
           _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
           || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L
       strndup():
           Since glibc 2.10:
               POSIX_C_SOURCE >= 200809L || _XOPEN_SOURCE >= 700
           Before glibc 2.10:
               _GNU_SOURCE
       strdupa(), strndupa(): _GNU_SOURCE

So I'd need to, eg, #define POSIX_C_SOURCE 200809L before the first #include.
see man 7 feature_test_macros