There are files like: ph

#ifndef P_H #define P_H #include <stdio.h> void p(); #endif

pc

 #include "ph" void p() { printf("Hello world\n"); }

hello.c

 #include "ph" int main() { p(); return 0; }

When compiling with the -o optimization option, everything is fine:

 gcc -c hello.c pc gcc hello.o po -o result

Problems occur when compiling with -o1 -o2 -o3 options

  gcc -c hello.c pc gcc hello.o po -o1 result result: In function `p': (.text+0x10b): multiple definition of `p' po:pc:(.text+0x0): first defined here result: In function `_fini': (.fini+0x0): multiple definition of `_fini' /usr/lib/gcc/x86_64-linux-gnu/4.9/../../../x86_64-linux-gnu/crti.o:/build/buildd/glibc-2.21/csu/../sysdeps/x86_64/crti.S:80: first defined here result: In function `data_start': (.data+0x0): multiple definition of `__data_start' /usr/lib/gcc/x86_64-linux-gnu/4.9/../../../x86_64-linux-gnu/crt1.o:(.data+0x0): first defined here result: In function `data_start': (.data+0x8): multiple definition of `__dso_handle' /usr/lib/gcc/x86_64-linux-gnu/4.9/crtbegin.o:(.data+0x0): first defined here result:(.rodata+0x0): multiple definition of `_IO_stdin_used' /usr/lib/gcc/x86_64-linux-gnu/4.9/../../../x86_64-linux-gnu/crt1.o:(.rodata.cst4+0x0): first defined here result: In function `_start': (.text+0x0): multiple definition of `_start' /usr/lib/gcc/x86_64-linux-gnu/4.9/../../../x86_64-linux-gnu/crt1.o:(.text+0x0): first defined here result: In function `main': (.text+0xf6): multiple definition of `main' hello.o:hello.c:(.text+0x0): first defined here result: In function `_init': (.init+0x0): multiple definition of `_init' /usr/lib/gcc/x86_64-linux-gnu/4.9/../../../x86_64-linux-gnu/crti.o:/build/buildd/glibc-2.21/csu/../sysdeps/x86_64/crti.S:64: first defined here /usr/lib/gcc/x86_64-linux-gnu/4.9/crtend.o:(.tm_clone_table+0x0): multiple definition of `__TMC_END__' result:(.data+0x10): first defined here /usr/bin/ld: ошибка в result(.eh_frame); таблиц .eh_frame_hdr создана не будет. collect2: error: ld returned 1 exit status

With Linux and gcc is not very familiar, what the problem is I do not understand.

  • If you are given an exhaustive answer, mark it as correct (a daw opposite the selected answer). - Nicolas Chabanovsky ♦

2 answers 2

-o имя is the name of the output file,
-O1 is an optimization option.

When you do

 gcc src.o -o result gcc src.o result -O1

You src.o file with the result file that was obtained in the previous step.
Naturally you will have all the names duplicated.

Write

 gcc -c -O2 hello.c pc gcc -O2 hello.o po -o result

or rather, use some kind of build system, like CMake.

    result is the name of the executable?

     gcc hello.o po -o1 result
    then fix on:
     gcc hello.o po -o result -O1