Posted By: Anonymous
I’m getting a number of these warnings when compiling a few binaries:
warning: incompatible implicit declaration of built-in function ‘strcpy’ warning: incompatible implicit declaration of built-in function ‘strlen’ warning: incompatible implicit declaration of built-in function ‘exit’
To try to resolve this, I have added
at the top of the C files associated with this warning, in addition to compiling with the following flags:
CFLAGS = -fno-builtin-exit -fno-builtin-strcat -fno-builtin-strncat -fno-builtin-strcpy -fno-builtin-strlen -fno-builtin-calloc
I am using GCC 4.1.2:
$ gcc --version gcc (GCC) 4.1.2 20080704
What should I do to resolve these warnings?
In C, using a previously undeclared function constitutes an implicit declaration of the function. In an implicit declaration, the return type is
int if I recall correctly. Now, GCC has built-in definitions for some standard functions. If an implicit declaration does not match the built-in definition, you get this warning.
To fix the problem, you have to declare the functions before using them; normally you do this by including the appropriate header. I recommend not to use the
-fno-builtin-* flags if possible.
Instead of stdlib.h, you should try:
strncpy are defined, at least according to the
strcpy(2) man page.
exit function is defined in stdlib.h, though, so I don’t know what’s going on there.