[bitlug] C Startup files...
- From: Peeyush Prasad <peeyush@xxxxxxxxxx>
- To: bitlug@xxxxxxxxxxxxx
- Date: Tue, 15 Nov 2005 10:08:08 +0530 (IST)
Hi again,
Thought I should start another thread for this discussion...
Does anybody know the functions of the various startup files ?
I see the following on my system: (RH 7.3, gcc 2.96)
/usr/lib/gcc-lib/i386-redhat-linux/2.96/crtbegin.o
/usr/lib/gcc-lib/i386-redhat-linux/2.96/crtbeginS.o
/usr/lib/gcc-lib/i386-redhat-linux/2.96/crtend.o
/usr/lib/gcc-lib/i386-redhat-linux/2.96/crtendS.o
and
/usr/lib/crt1.o
/usr/lib/crti.o
/usr/lib/crtn.o
These guys get linked in if you do a default gcc build with the c
library:
Best thing to do is to find the files in the gcc sources and go through
them, but I want to stay away from that....
Now,lets see...
[vlbi@rcs1 bfin]$ cat hello.c
#include <stdio.h>
int main(int argc,char *argv[])
{
int i = 0;
for(i=0; i<10; i++)
printf("Go AwaY!! >:-(\n");
getchar();
return 0;
}
[vlbi@rcs1 bfin]$ gcc -v -o hello hello.c
Reading specs from /usr/lib/gcc-lib/i386-redhat-linux/2.96/specs
gcc version 2.96 20000731 (Red Hat Linux 7.3 2.96-110)
/usr/lib/gcc-lib/i386-redhat-linux/2.96/cpp0 -lang-c -v -D__GNUC__=2
-D__GNUC_MINOR__=96 -D__GNUC_PATCHLEVEL__=0 -D__ELF__ -Dunix -Dlinux
-D__ELF__ -D__unix__ -D__linux__ -D__unix -D__linux -Asystem(posix)
-D__NO_INLINE__ -Acpu(i386) -Amachine(i386) -Di386 -D__i386 -D__i386__
-D__tune_i386__ hello.c /tmp/ccLkKeK6.i
GNU CPP version 2.96 20000731 (Red Hat Linux 7.3 2.96-110) (cpplib) (i386
Linux/ELF)
ignoring nonexistent directory "/usr/i386-redhat-linux/include"
#include "..." search starts here:
#include <...> search starts here:
/usr/local/include
/usr/lib/gcc-lib/i386-redhat-linux/2.96/include
/usr/include
End of search list.
// =========== Compile command ==============
/usr/lib/gcc-lib/i386-redhat-linux/2.96/cc1 /tmp/ccLkKeK6.i -quiet
-dumpbase hello.c -version -o /tmp/ccu7NLr5.s
GNU C version 2.96 20000731 (Red Hat Linux 7.3 2.96-110)
(i386-redhat-linux) compiled by GNU C version 2.96 20000731 (Red Hat Linux
7.3 2.96-110).
// ========== Assemble command ==============
as -V -Qy -o /tmp/ccpaFlN5.o /tmp/ccu7NLr5.s
GNU assembler version 2.11.93.0.2 (i386-redhat-linux) using BFD version
2.11.93.0.2 20020207
// ========== Linker called from within the assembler =========
/usr/lib/gcc-lib/i386-redhat-linux/2.96/collect2 -m elf_i386
-dynamic-linker /lib/ld-linux.so.2 -o hello
/usr/lib/gcc-lib/i386-redhat-linux/2.96/../../../crt1.o
/usr/lib/gcc-lib/i386-redhat-linux/2.96/../../../crti.o
/usr/lib/gcc-lib/i386-redhat-linux/2.96/crtbegin.o
-L/usr/lib/gcc-lib/i386-redhat-linux/2.96
-L/usr/lib/gcc-lib/i386-redhat-linux/2.96/../../.. /tmp/ccpaFlN5.o -lgcc
-lc -lgcc /usr/lib/gcc-lib/i386-redhat-linux/2.96/crtend.o
/usr/lib/gcc-lib/i386-redhat-linux/2.96/../../../crtn.o
[vlbi@rcs1 vlbi]$ pgrep hello
20713
[vlbi@rcs1 vlbi]$ cat /proc/20713/
cmdline cwd exe maps mounts stat status
cpu environ fd mem root statm
[vlbi@rcs1 vlbi]$ cat /proc/20713/mem
cat: /proc/20713/mem: No such process
[vlbi@rcs1 vlbi]$ cat /proc/20713/maps
08048000-08049000 r-xp 00000000 03:05 229541 /home/vlbi/bfin/hello
08049000-0804a000 rw-p 00000000 03:05 229541 /home/vlbi/bfin/hello
40000000-40013000 r-xp 00000000 03:07 67421 /lib/ld-2.2.5.so
40013000-40014000 rw-p 00013000 03:07 67421 /lib/ld-2.2.5.so
40014000-40016000 rw-p 00000000 00:00 0
42000000-4212c000 r-xp 00000000 03:07 114259 /lib/i686/libc-2.2.5.so
4212c000-42131000 rw-p 0012c000 03:07 114259 /lib/i686/libc-2.2.5.so
42131000-42135000 rw-p 00000000 00:00 0
bfffe000-c0000000 rwxp fffff000 00:00 0
Questions:
1. What is cpp0?
2. What does collect2 do ??
3. The following are linked in: crt1.o crti.o crtbegin.o crtend.o crtn.o
-lc -lgcc. Why??
4. The dynamic linker ? /lib/ld-linux.so.2 ??
-- P
ps - output :^)
[vlbi@rcs1 bfin]$ ./hello
Go AwaY!! >:-(
Go AwaY!! >:-(
Go AwaY!! >:-(
Go AwaY!! >:-(
Go AwaY!! >:-(
Go AwaY!! >:-(
Go AwaY!! >:-(
Go AwaY!! >:-(
Go AwaY!! >:-(
Go AwaY!! >:-(
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