[patch] Do not generate discriminator directive in strict mode

[patch] Do not generate discriminator directive in strict mode

[Eric Botcazou]

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Hi,

it appears that the (standard DWARF as of version 4) discriminator directive 
can confuse non-GDB DWARF 2/3 debuggers, so this patch changes the compiler 
to stop emitting it in strict mode.

Tested on i586-suse-linux, OK for the mainline?


2011-04-19  Eric Botcazou  <ebotcazou@adacore.com>

	* dwarf2out.c (dwarf2out_source_line): Emit "discriminator" directive
	only for version 4 or above, or else in non-strict mode.


-- 
Eric Botcazou

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Index: dwarf2out.c
===================================================================
--- dwarf2out.c	(revision 172693)
+++ dwarf2out.c	(working copy)
@@ -22232,7 +22240,9 @@ dwarf2out_source_line (unsigned int line
       fprintf (asm_out_file, "\t.loc %d %d 0", file_num, line);
       if (is_stmt != table->is_stmt)
 	fprintf (asm_out_file, " is_stmt %d", is_stmt ? 1 : 0);
-      if (SUPPORTS_DISCRIMINATOR && discriminator != 0)
+      if (SUPPORTS_DISCRIMINATOR
+	  && discriminator != 0
+	  && (dwarf_version >= 4 || !dwarf_strict))
 	fprintf (asm_out_file, " discriminator %d", discriminator);
       fputc ('\n', asm_out_file);
     }

Re: [patch] Do not generate discriminator directive in strict mode

[Richard Henderson]

On 04/19/2011 06:40 AM, Eric Botcazou wrote:
> -      if (SUPPORTS_DISCRIMINATOR && discriminator != 0)
> +      if (SUPPORTS_DISCRIMINATOR
> +	  && discriminator != 0
> +	  && (dwarf_version >= 4 || !dwarf_strict))
>  	fprintf (asm_out_file, " discriminator %d", discriminator);

How is this not redundant with the existing

  /* The discriminator column was added in dwarf4.  Simplify the below
     by simply removing it if we're not supposed to output it.  */
  if (dwarf_version < 4 && dwarf_strict)
    discriminator = 0;

check near the top of the function?


r~

Re: [patch] Do not generate discriminator directive in strict mode

[Eric Botcazou]

> How is this not redundant with the existing
>
>   /* The discriminator column was added in dwarf4.  Simplify the below
>      by simply removing it if we're not supposed to output it.  */
>   if (dwarf_version < 4 && dwarf_strict)
>     discriminator = 0;
>
> check near the top of the function?

Obviously I missed this recent change, sorry.  So the question is: would the 
change be appropriate for the release branches, where we emit the directive 
unconditionally, i.e 4.5 and 4.6 branches, or would mine be safer for them?  
This directive apparently confuses (some versions of) the Wind River debugger.

-- 
Eric Botcazou

Re: [patch] Do not generate discriminator directive in strict mode

[Richard Henderson]

On 04/20/2011 12:09 PM, Eric Botcazou wrote:
>> How is this not redundant with the existing
>>
>>   /* The discriminator column was added in dwarf4.  Simplify the below
>>      by simply removing it if we're not supposed to output it.  */
>>   if (dwarf_version < 4 && dwarf_strict)
>>     discriminator = 0;
>>
>> check near the top of the function?
> 
> Obviously I missed this recent change, sorry.  So the question is: would the 
> change be appropriate for the release branches, where we emit the directive 
> unconditionally, i.e 4.5 and 4.6 branches, or would mine be safer for them?

Let's try to keep the branches more similar than not.  It's just as safe, since
prior to mainline we ignore the discriminator when not emitting via gas directive.


r~