CODEWITHSUNDEEP
glibclibc
Jay
Jay

Reputation: 1038

Where is "generic_start_main()" defined?

I got a segmentation fault from running a program. The backtrace command in gdb shows that the calling stack is 

#0  0x000000001048d594 in .__libc_csu_init ()
#1  0x000000001048ce20 in .generic_start_main ()
#2  0x000000001048d030 in .__libc_start_main ()
#3  0x0000000000000000 in ?? ()

Can someone tell me where generic_start_main() is defined? I tried to search in glibc with grep -R generic_start_main * but only got 

sysdeps/unix/sysv/linux/powerpc/libc-start.c:29:#define LIBC_START_MAIN generic_start_main
sysdeps/unix/sysv/linux/powerpc/libc-start.c:102:  return generic_start_main (stinfo->main, argc, argv, auxvec,

I'm running programs on a 3.10.0 Linux on a 64-bit PowerPC machine.

Upvotes: 2

Views: 759

Answers (1)

Employed Russian
Employed Russian

Reputation: 213446

but only got

You give up too easily. Look in sysdeps/unix/sysv/linux/powerpc/libc-start.c, and you'll see that it #include <csu/libc-start.c> after defining LIBC_START_MAIN, and the csu/libc-start.c has:

STATIC int
LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
                  int argc, char **argv,
#ifdef LIBC_START_MAIN_AUXVEC_ARG
                  ElfW(auxv_t) *auxvec,
#endif
                  __typeof (main) init,
                  void (*fini) (void),
                  void (*rtld_fini) (void), void *stack_end)
 { ...

Update:

I'm not very familiar with how the #define macro works.

The #define creates a text substitution rule for the preprocessor. For example:

#define FOO Bar

tells the preprocessor: every time you see FOO, replace it with Bar (there are some details I am sweeping under the rug here, but they are not important for this question).

So, given:

#define LIBC_START_MAIN generic_start_main
int LIBC_START_MAIN() { ... }

This is what the compiler sees after preprocessing:

int generic_start_main() { ... }

Upvotes: 1

Related Questions