[Bug breakpoints/30215] GDB cannot hit second time in empty while loop

["tromey at sourceware dot org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=30215

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tromey at sourceware dot org

--- Comment #1 from Tom Tromey <tromey at sourceware dot org> ---
The Fedora 36 gcc has this issue.
Look at my source and the decodedline dump:

murgatroyd. nl -ba q.c
     1  void foo(void) 
     2  {
     3  int a = 1;
     4  while(a);
     5  }
murgatroyd. readelf --debug-dump=decodedline q.o 
Contents of the .debug_line section:

CU: ./q.c:
File name                            Line number    Starting address    View   
Stmt
q.c                                            2                   0           
   x
q.c                                            3                 0x4           
   x
q.c                                            4                 0xb           
   x
q.c                                            4                 0xc           
   x
q.c                                            5                0x12           
   x
q.c                                            -                0x16


Now the disassembly:

0000000000000000 <foo>:
   0:   55                      push   %rbp
   1:   48 89 e5                mov    %rsp,%rbp
   4:   c7 45 fc 01 00 00 00    movl   $0x1,-0x4(%rbp)
   b:   90                      nop
   c:   83 7d fc 00             cmpl   $0x0,-0x4(%rbp)
  10:   75 fa                   jne    c <foo+0xc>
...

Both 0xb and 0xc are marked as statements.
However when setting a breakpoint, I think gdb picks the lowest address.

So on the one hand, maybe this is a gdb bug.
Perhaps it should set a low-level breakpoint at each instruction that is
marked as being a statement at the given line.  The idea being, if a given
statement has multiple "entry points", gdb should catch them all.  These
would have to be spots where stepping would stop as well.

On the other hand, IMO this behavior by the compiler is pathological.

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