[PATCH] gdb/testsuite: make declare_labels use better default label names

[PATCH] gdb/testsuite: make declare_labels use better default label names

[Simon Marchi]

When using the single-element form of argument to declare_labels, the
generated label (in the assembly file) is of the format ".LlabelN",
where N is a number.

I propose making it use the name of the label by default.  Calling:

    declare_labels foo

will generate the ".LfooN" in the assembly file (again, where N is a
number).  When debugging the output of the DWARF assembler, it makes it
easier to map labels to the source.  Also, when defining the same label
twice by mistake in the Tcl code (like I d id), it's easier to track the
error from the message to the root cause:

    -/home/smarchi/build/binutils-gdb/gdb/testsuite/outputs/gdb.dwarf2/implptrpiece/implptrpiece-dw.S:62: Error: symbol `.Llabel5' is already defined
    +/home/smarchi/build/binutils-gdb/gdb/testsuite/outputs/gdb.dwarf2/implptrpiece/implptrpiece-dw.S:62: Error: symbol `.Lvar_label5' is already defined

This doesn't change anything for the test cases, it just makes the
assembly output a bit nicer.

gdb/testsuite/ChangeLog:

	* lib/dwarf.exp (declare_labels): Use name as text if text is
	not provided.

Change-Id: I63856c1fa6390498fd5b9d66f471f817ff0a465c
---
 gdb/testsuite/lib/dwarf.exp | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/gdb/testsuite/lib/dwarf.exp b/gdb/testsuite/lib/dwarf.exp
index c1596df58be..ecd438b205e 100644
--- a/gdb/testsuite/lib/dwarf.exp
+++ b/gdb/testsuite/lib/dwarf.exp
@@ -863,13 +863,13 @@ namespace eval Dwarf {
 	    set name [lindex $arg 0]
 	    set text [lindex $arg 1]
 
-	    upvar $name label_var
-	    if {$text == ""} {
-		set label_var [new_label]
-	    } else {
-		set label_var [new_label $text]
+	    if { $text == "" } {
+		set text $name
 	    }
 
+	    upvar $name label_var
+	    set label_var [new_label $text]
+
 	    proc ${name}: {args} [format {
 		define_label %s
 		uplevel $args
-- 
2.29.2

Re: [PATCH] gdb/testsuite: make declare_labels use better default label names

[Tom Tromey]

>>>>> "Simon" == Simon Marchi via Gdb-patches <gdb-patches@sourceware.org> writes:

Simon> When using the single-element form of argument to declare_labels, the
Simon> generated label (in the assembly file) is of the format ".LlabelN",
Simon> where N is a number.

Simon> I propose making it use the name of the label by default.  Calling:

Simon>     declare_labels foo

Simon> will generate the ".LfooN" in the assembly file (again, where N is a
Simon> number).

Seems like a good idea to me.

Simon> Also, when defining the same label
Simon> twice by mistake in the Tcl code (like I d id)

Can we make this a Tcl error at the point of redefinition?
For example declare_labels and define_label could use a new
namespace-local array to track when labels are declared and when they
are defined, to prevent non-declaration (if that is needed, I forget)
and redefinition.

Simon> gdb/testsuite/ChangeLog:

Simon> 	* lib/dwarf.exp (declare_labels): Use name as text if text is
Simon> 	not provided.

Looks good.

Tom

Re: [PATCH] gdb/testsuite: make declare_labels use better default label names

[Simon Marchi]

On 2020-12-04 2:46 p.m., Tom Tromey wrote:
>>>>>> "Simon" == Simon Marchi via Gdb-patches <gdb-patches@sourceware.org> writes:
>
> Simon> When using the single-element form of argument to declare_labels, the
> Simon> generated label (in the assembly file) is of the format ".LlabelN",
> Simon> where N is a number.
>
> Simon> I propose making it use the name of the label by default.  Calling:
>
> Simon>     declare_labels foo
>
> Simon> will generate the ".LfooN" in the assembly file (again, where N is a
> Simon> number).
>
> Seems like a good idea to me.
>
> Simon> Also, when defining the same label
> Simon> twice by mistake in the Tcl code (like I d id)
>
> Can we make this a Tcl error at the point of redefinition?
> For example declare_labels and define_label could use a new
> namespace-local array to track when labels are declared and when they
> are defined, to prevent non-declaration (if that is needed, I forget)
> and redefinition.

That would be nice indeed.

>
> Simon> gdb/testsuite/ChangeLog:
>
> Simon> 	* lib/dwarf.exp (declare_labels): Use name as text if text is
> Simon> 	not provided.
>
> Looks good.

Thanks, I'll merge this.  Even if the TCL code tracks declared labels to
check for duplication, it still sounds nice to have assembly label name
matching the TCL label names.

Simon