[Bug debug/98776] DW_AT_low_pc is inconsistent with function entry address, when enabling -fpatchable-function-entry

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98776

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Martin Liška from comment #5)
> (In reply to Richard Biener from comment #4)
> > Martin, can you bisect what fixed it?
> 
> Sure. Please help me how to verify what is a correct output? Isn't that
> related to DWARF 5 change done in GCC 11?

It's consistent with -gdwarf-2 -gstrict-dwarf as well, so no.

A broken executable will output a short disassembly from gdb:


> gcc-10 t.c -g -O -fpatchable-function-entry=16
> gdb -ex 'disassemble foo' -batch ./a.out | wc -l
3

actual output is

Dump of assembler code for function foo:
   0x00000000004004a6 <+0>:     ret    
End of assembler dump.

where a correctly working one is

> gdb -ex 'disassemble foo' -batch ./a.out | wc -l
19

with output

Dump of assembler code for function foo:
   0x0000000000400476 <+0>:     nop
   0x0000000000400477 <+1>:     nop
   0x0000000000400478 <+2>:     nop
   0x0000000000400479 <+3>:     nop
   0x000000000040047a <+4>:     nop
   0x000000000040047b <+5>:     nop
   0x000000000040047c <+6>:     nop
   0x000000000040047d <+7>:     nop
   0x000000000040047e <+8>:     nop
   0x000000000040047f <+9>:     nop
   0x0000000000400480 <+10>:    nop
   0x0000000000400481 <+11>:    nop
   0x0000000000400482 <+12>:    nop
   0x0000000000400483 <+13>:    nop
   0x0000000000400484 <+14>:    nop
   0x0000000000400485 <+15>:    nop
   0x0000000000400486 <+16>:    ret    
End of assembler dump.