incompatible redeclaration of library function

Clang Frontend
1

I'm having the following warning, when trying to compile standard
library functions, like strlen, memset, etc.

warning: incompatible redeclaration of library function 'strlen'

size_t strlen(const char *s);
       ^
note: 'strlen' is a builtin with type 'unsigned int (char const *)'

size_t is a typedef for unsigned long. clang CFLAGS include -std=c99
-nostdlib -nostdinc

I'm not sure how to solve this. It would be useful if size_t were
defined as unsigned long. Any advice ?

2

clang internally defines size_t according to the selected target;
what's your CPU/OS? Or are you trying to do something unusual?
(-fno-builtin will get rid of this warning, but it's kind of overkill
in this case).

-Eli

3

This is almost good to me, however there are some parts of the
library (ie, in printf) that require the use of the equivalent signed
version of size_t (for example, to print the argument "%zd"). Is there
a way to get this in clang ? Else, I'll have to define size_t in per
case basis. Same for ptrdiff_t.

Ah... that's kind of messy. If you make the assumption that size_t
and ptrdiff_t are either short, int, long, or long long, you can
probably pull it off with a combination of typeof,
__builtin_choose_expr, and __builtin_types_compatible_p.

Also, what's the expected behavior of redefining a built-in function ?

Redeclaring a built-in function with a compatible prototype is okay.
If you need to define library functions, you should pass in
-fno-builtin on the command-line.

-Eli