[PING][PATCH 1/2] Allow function prologues to have multiple repeating lines

[Alan Hayward <Alan dot Hayward at arm dot com>]

Ping for this and part two.

There was no 0/2. Thinking about it now, I probably should have said:


[0/2] Fix start line for function breakpoints on Ubuntu

These two patches came out of the change I made to ovldbreak.exp due to the
breakpoint at main starting on the { instead of the first line. This happens
only on Ubuntu.

Part one is a generic fix. Part two is an addition to the fix specifically
for i386/amd64. Part two also reverts the line number part of ovldbreak.exp.

Fixes roughly 50 test cases for Ubuntu.

Alan.



> On 24 Oct 2018, at 10:04, Alan Hayward <Alan.Hayward@arm.com> wrote:
> 
> Compiling gdb.cp/ovldbreak.cc on Ubuntu places two identical line numbers
> in the function prologue.
> 
> x86_64 Ubtunu 16.04 with GCC 5.4.0-6ubuntu1~16.04.4
> 000000000040052f <main>:
> Line 48
>  40052f:	55                   	push   %rbp
>  400530:	48 89 e5             	mov    %rsp,%rbp
>  400533:	53                   	push   %rbx
>  400534:	48 81 ec 88 00 00 00 	sub    $0x88,%rsp
> Line 48
>  40053b:	64 48 8b 04 25 28 00 	mov    %fs:0x28,%rax
>  400542:	00 00
>  400544:	48 89 45 e8          	mov    %rax,-0x18(%rbp)
>  400548:	31 c0                	xor    %eax,%eax
> Line 49
>  40054a:	c6 45 85 02          	movb   $0x2,-0x7b(%rbp)
> Line 50
>  40054e:	c6 45 86 03          	movb   $0x3,-0x7a(%rbp)
> etc
> 
> Aarch64 Ubuntu 16.04 with GCC 7.2.0-1ubuntu1~16.04
> 0000000000400708 <main>:
> Line 48
>  400708:	d102c3ff 	sub	sp, sp, #0xb0
>  40070c:	a9027bfd 	stp	x29, x30, [sp,#32]
>  400710:	910083fd 	add	x29, sp, #0x20
>  400714:	f9001bf3 	str	x19, [sp,#48]
> Line 48
>  400718:	90000100 	adrp	x0, 420000 <_GLOBAL_OFFSET_TABLE_+0x28>
>  40071c:	9100e000 	add	x0, x0, #0x38
>  400720:	f9400001 	ldr	x1, [x0]
>  400724:	f90047a1 	str	x1, [x29,#136]
>  400728:	d2800001 	mov	x1, #0x0                   	// #0
> Line 49
>  40072c:	52800040 	mov	w0, #0x2                   	// #2
>  400730:	3900b7a0 	strb	w0, [x29,#45]
> Line 50
>  400734:	52800060 	mov	w0, #0x3                   	// #3
>  400738:	3900bba0 	strb	w0, [x29,#46]
> etc
> 
> Compare to openSUSE 13.3 AArch64 with GCC 7.2.1 20171020
> 
> 00000000004005e4 <main>:
> Line 48
>  4005e4:	d102c3ff 	sub	sp, sp, #0xb0
>  4005e8:	a9027bfd 	stp	x29, x30, [sp, #32]
>  4005ec:	910083fd 	add	x29, sp, #0x20
>  4005f0:	f9001bf3 	str	x19, [sp, #48]
> Line 49
>  4005f4:	52800040 	mov	w0, #0x2                   	// #2
>  4005f8:	39023fa0 	strb	w0, [x29, #143]
> Line 50
>  4005fc:	52800060 	mov	w0, #0x3                   	// #3
>  400600:	39023ba0 	strb	w0, [x29, #142]
> 
> skip_prologue_using_sal () does did not allow for the case where there might
> be two SALs with the same line number in a function prologue. Allow this.
> 
> Fixes over 50 tests on Aarch64 Ubuntu.
> 
> 2018-10-24  Alan Hayward  <alan.hayward@arm.com>
> 
> 	* symtab.c (skip_prologue_using_sal): Don't break for equal line
> 	numbers.
> ---
> gdb/symtab.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/gdb/symtab.c b/gdb/symtab.c
> index 2e48d6527e..67ab5d40fa 100644
> --- a/gdb/symtab.c
> +++ b/gdb/symtab.c
> @@ -3925,9 +3925,9 @@ skip_prologue_using_sal (struct gdbarch *gdbarch, CORE_ADDR func_addr)
> 	  sal = find_pc_line (prologue_sal.end, 0);
> 	  if (sal.line == 0)
> 	    break;
> -	  /* Assume that a consecutive SAL for the same (or larger)
> -	     line mark the prologue -> body transition.  */
> -	  if (sal.line >= prologue_sal.line)
> +	  /* Assume that a SAL to a larger line marks the prologue -> body
> +	     transition.  */
> +	  if (sal.line > prologue_sal.line)
> 	    break;
> 	  /* Likewise if we are in a different symtab altogether
> 	     (e.g. within a file included via #include).  */
> -- 
> 2.17.1 (Apple Git-112)
>