[Bug debug/19191] New: No DWARF2 DW_TAG_inlined_subroutine entry generated

["gcc-bugzilla at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

The current gcc 4 development compiler does not generate DWARF2
DW_TAG_inlined_subroutine entries for concrete instances of inlined
subroutines.  The correct entries are generated by the compiler
included in Fedora Core 3, which identifies itself as "gcc version
3.4.2 20041017 (Red Hat 3.4.2-6.fc3)".

Environment:
System: Linux toadfish.ninemoons.com 2.6.9-1.681_FC3.stk16 #1 Mon Nov 22 16:44:32 EST 2004 i686 i686 i386 GNU/Linux
Architecture: i686

	
host: i686-pc-linux-gnu
build: i686-pc-linux-gnu
target: i686-pc-linux-gnu
configured with: /src/sourceware/gcc/gcc/configure -v --prefix=/opt/local/sourceware --with-gcc-version-trigger=/src/sourceware/gcc/gcc/gcc/version.c --enable-languages=c,c++

How-To-Repeat:

Given the test case:

  int add2 (int a, int b)
  {
    return (a + b);
  }
  
  inline int add3 (int a, int b, int c)
  {
    return (a + add2 (b , c));
  }
  
  main ()
  {
    printf ("%d\n", add3 (2, 3, 4));
  }
  
Run:

  gcc -g -O2 --save-temps -o t t.c
  readelf --debug-dump t >t.dwarf
  objdump --disassemble t >t.dis

For the Fedora core 3 compiler, there will be some entries in t.dwarf
that look like:

 <2><ec>: Abbrev Number: 13 (DW_TAG_inlined_subroutine)
          DW_AT_abstract_origin: <5f>	
          DW_AT_low_pc      : 0x8048398	
          DW_AT_high_pc     : 0x80483a4	
 <3><f9>: Abbrev Number: 14 (DW_TAG_formal_parameter)
          DW_AT_abstract_origin: <a0>	
 <3><fe>: Abbrev Number: 14 (DW_TAG_formal_parameter)
          DW_AT_abstract_origin: <a8>	
 <3><103>: Abbrev Number: 14 (DW_TAG_formal_parameter)
          DW_AT_abstract_origin: <b0>	

For the inlined code marked with '***' below:

       0804838c <main>:
        804838c:   55                      push   %ebp
        804838d:   89 e5                   mov    %esp,%ebp
        804838f:   83 ec 08                sub    $0x8,%esp
        8048392:   83 e4 f0                and    $0xfffffff0,%esp
        8048395:   83 ec 10                sub    $0x10,%esp
***     8048398:   6a 04                   push   $0x4
***     804839a:   6a 03                   push   $0x3
***     804839c:   e8 c7 ff ff ff          call   8048368 <add2>
***     80483a1:   83 c0 02                add    $0x2,%eax
        80483a4:   50                      push   %eax
        80483a5:   68 94 84 04 08          push   $0x8048494
        80483aa:   e8 01 ff ff ff          call   80482b0 <printf@plt>
        80483af:   c9                      leave  
        80483b0:   c3                      ret    

As a side note, the inlined code generated by the 4.0.0 compiler
is not contiguous, as marked with '***' below:
  
       080483a0 <main>:
        80483a0:   55                      push   %ebp
***     80483a1:   b8 04 00 00 00          mov    $0x4,%eax
        80483a6:   89 e5                   mov    %esp,%ebp
        80483a8:   83 ec 08                sub    $0x8,%esp
        80483ab:   83 e4 f0                and    $0xfffffff0,%esp
        80483ae:   83 ec 10                sub    $0x10,%esp
***     80483b1:   89 44 24 04             mov    %eax,0x4(%esp)
***     80483b5:   c7 04 24 03 00 00 00    movl   $0x3,(%esp)
***     80483bc:   e8 af ff ff ff          call   8048370 <add2>
        80483c1:   c7 04 24 c8 84 04 08    movl   $0x80484c8,(%esp)
***     80483c8:   83 c0 02                add    $0x2,%eax
        80483cb:   89 44 24 04             mov    %eax,0x4(%esp)
        80483cf:   e8 dc fe ff ff          call   80482b0 <printf@plt>
        80483d4:   c9                      leave  
        80483d5:   c3                      ret    

The DWARF2 spec says this about subroutines:

  Note that for the low and high pc attributes to have meaning, DWARF
  makes the assumption that the code for a single subroutine is
  allocated in a single contiguous block of memory.

However the draft DWARF3 spec, which has new support for
non-contiguous address ranges, says this:

  The presence of low and high PC attributes for an entity implies that
  the code generated for the entity is contiguous and exists totally
  within the boundaries specified by those two attributes. If that is
  not the case, no low and high PC attributes should be produced.

In DWARF3, you are supposed to use the DW_AT_ranges attribute to
describe a non-contiguous range of addresses.  From looking at
dwarf2out.c in the compiler sources, it appears that there is some
support for the DW_AT_ranges attribute already in gcc.

-- 
           Summary: No DWARF2 DW_TAG_inlined_subroutine entry generated
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: fnf at specifixinc dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19191