[Bug other/70428] New: -fdebug-prefix-map did not support to remap sources with relative path

["hongxu.jia at windriver dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70428

            Bug ID: 70428
           Summary: -fdebug-prefix-map did not support to remap sources
                    with relative path
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hongxu.jia at windriver dot com
  Target Milestone: ---

1. Prepare sources and build dir

$ pwd
/folk/hjia

$ mkdir dir1/dir2 test1/test2/ -p

$ cat > test1/test2/test.c << ENDOF
#include "test.h"

int main(int argc, char *argv[])
{
  func();
  return 0;
}

ENDOF

$ cat > test1/test2/test.h << ENDOF
void func()
{
  return;
}
ENDOF

$ cd dir1/dir2

2. Enter build dir to compile with relative path sources

$ gcc ../../test1/test2/test.c -g  -o test.o
$ objdump -g test.o | less
----------------
 <0><b>: Abbrev Number: 1 (DW_TAG_compile_unit)
    <c>   DW_AT_producer    : (indirect string, offset: 0x47): GNU C 4.8.4
-mtune=generic -march=x86-64 -g -fstack-protector    
    <10>   DW_AT_language    : 1        (ANSI C)
    <11>   DW_AT_name        : (indirect string, offset: 0x5):
../../test1/test2/test.c 
    <15>   DW_AT_comp_dir    : (indirect string, offset: 0x1e):
/folk/hjia/dir1/dir2

Contents of the .debug_str section:
----------------

3. Compile with option -fdebug-prefix-map, it could not remap sources with
relative path

$ gcc ../../test1/test2/test.c
-fdebug-prefix-map=/folk/hjia/test1/test2=/usr/src -g  -o test.o
$ objdump -g test.o | less
----------------
 <0><b>: Abbrev Number: 1 (DW_TAG_compile_unit)
    <c>   DW_AT_producer    : (indirect string, offset: 0x47): GNU C 4.8.4
-mtune=generic -march=x86-64 -g
-fdebug-prefix-map=/folk/hjia/test1/test2=/usr/src -fstack-protector 
    <10>   DW_AT_language    : 1        (ANSI C)
    <11>   DW_AT_name        : (indirect string, offset: 0x5):
../../test1/test2/test.c 
    <15>   DW_AT_comp_dir    : (indirect string, offset: 0x1e):
/folk/hjia/dir1/dir2 
----------------

What we expected is:
----------------
    <11>   DW_AT_name        : (indirect string, offset: 0x5): /usr/src/test.c  
    <15>   DW_AT_comp_dir    : (indirect string, offset: 0x15):
/folk/hjia/dir1/dir2
----------------