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Date: Mon, 13 Mar 2000 14:24:09 -0600
From: Oscar Bonilla <obonilla@fisicc-ufm.edu>
To: Marco van de Voort <marcov@stack.nl>
Cc: freebsd-hackers@FreeBSD.ORG
Subject: Re: inner workings of the C compiler
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On Sat, Mar 11, 2000 at 02:30:19PM +0100, Marco van de Voort wrote:
> P.s. Could you sent me a minimal C program linking to libc, and the
> commandline to compile it with -nostdlib ?
>
> I could throw all these experiences with non standard linking in a
> little tex doc.  ( --nostdlib with and without libc, pure assembler
> instead of c (no gcc), some small chapter about syscall conventions
> etc)

Here's what I have for a test program:

-----
#include <stdio.h>
#include <sys/types.h>
#include <pwd.h>

int main () {

    struct passwd *password;

    while ( (password = getpwent()) != NULL ) {
	printf("login: %s\n", password->pw_name);
    }

    password = getpwnam("root");
    printf("root has uid: %d\n", password->pw_uid);

    password = getpwuid(0);
    printf("uid 0 is %s\n", password->pw_name);
    
    return 0;
}
-----

I copied /usr/src/lib/libc and /usr/src/lib/csu to the parent dir of
this test, and thus my makefile is:

-----
all: get-test

get-test.o: get-test.c
	cc -g -Wall -pedantic -ansi -c -I../libc/include get-test.c

get-test: get-test.o
	cc -g -nostdlib -static -L../libc -o get-test \
	../csu/i386-elf/crt1.o \
	../csu/i386-elf/crti.o \
	../csu/i386-elf/crtbegin.o \
	get-test.o \
	../csu/i386-elf/crtend.o \
	../csu/i386-elf/crtn.o \
	-lc

clean:
	rm -f nss-test get-test *.o *.core *.*~
-----

The ordering above was pointed to me by Chuck Robey who got it using
the -v flag to cc (which shows you what the C compiler is doing to get
good links).

I'm not 100% sure that the -lc should be at the end... more likely it
should be right after (before?) my object file (get-test.o), but it
seems to work both ways.

regards,

-oscar

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