Problems with ld, libc, and "struct stat"

[David Demelier]

Le 15/10/2019 à 20:44, Jan Behrens a écrit :
> Hello,
> 
> I stumbled across a weird problem related stat() that (according to my
> research) seems to be related to an update of the "struct stat"
> C-structure in recent Kernel versions.
> 
> Consider the following two files.
> 
> testlib.c:
> #include <sys/stat.h>
> #include <stdio.h>
> void testfunc() {
>    struct stat sb;
>    stat("testlib.c", &sb);
>    printf("Size of testlib.c is %i bytes.\n", (int)sb.st_size);
> }

Please test the result of stat otherwise sb is left untouched (so all 
member undefined).

> testprog.c:
> extern void testfunc(void);
> int main(int argc, char **argv) {
>    testfunc();
>    return 0;
> }
> 
> Now I run:
> 
> % cc -Wall -c -fPIC -o testlib.o testlib.c
> % cc -Wall -o testprog testlib.o testprog.c
> % ./testprog
> Size of testlib.c is 168 bytes.
> 
> But when I make a shared library like this, I get a different result:
> 
> % ld -shared -o testlib.so testlib.o

Hmm, we usually never call the linker itself when creating shared libraries.

Try instead: cc -shared -o testlib.so testlib.o

HTH

-- 
David