Re: [PATCH] Fix gdb.dwarf2/dwz.exp for thumb mode

[Yao Qi <yao at codesourcery dot com>]

Yao Qi <yao@codesourcery.com> writes:

> -if { $main_length == "" } {
> +set main_label_offset ""
> +set test "p main_label"
> +gdb_test_multiple $test $test {
> +    -re ".* = {.*} $hex <main\\+($decimal)>.*\r\n$gdb_prompt $" {
> +	set main_label_offset $expect_out(1,string)
> +    }
> +}

Here is the V3 of this patch, to address Andreas's comments about
getting the offset of main_label to main.

-- 
Yao (éå)
From: Yao Qi <yao@codesourcery.com>
Date: Sat, 13 Sep 2014 14:51:04 +0800
Subject: [PATCH] Fix gdb.dwarf2/dwz.exp for thumb mode

We see the fail in gdb.dwarf2/dwz.exp in thumb mode,

p the_int^M
$2 = 99^M
(gdb) FAIL: gdb.dwarf2/dwz.exp: p the_int

In thumb mode, the lsb of references to 'main' in the assembly
(produced by dwarf assember) is set, so the generated debug
information is incorrect.

in this patch, we add a label main_label inside function main.  Linker
doesn't set its lsb in thumb mode, and we can get function main's
address by 'main_label - $main_label_offset'.  This label isn't moved
out of function main in both gcc and clang.

gdb/testsuite:

2014-09-15  Yao Qi  <yao@codesourcery.com>

	* gdb.dwarf2/main.c (main): New lable main_label.
	* gdb.dwarf2/dwz.exp: Get the offset of main_label to main.
	Return early if $main_label_offset is unknown.  Get address
	of main by "main_label - $main_label_offset".

diff --git a/gdb/testsuite/gdb.dwarf2/dwz.exp b/gdb/testsuite/gdb.dwarf2/dwz.exp
index 9175f9e..3cf4e4f 100644
--- a/gdb/testsuite/gdb.dwarf2/dwz.exp
+++ b/gdb/testsuite/gdb.dwarf2/dwz.exp
@@ -27,8 +27,9 @@ if  {[gdb_compile ${srcdir}/${subdir}/${srcfile} ${binfile}1.o \
     return -1
 }
 
-# Start GDB and load object file, compute the function length which is
-# needed in the Dwarf Assembler below.
+# Start GDB and load object file, compute the function length and the
+# offset from main to main_label which are needed in the Dwarf Assembler
+# below.
 clean_restart ${testfile}1.o
 
 set main_length ""
@@ -59,9 +60,17 @@ gdb_test_multiple $test $test {
     }
 }
 
-if { $main_length == "" } {
+set main_label_offset ""
+set test "p main_label - main"
+gdb_test_multiple $test $test {
+    -re ".* = ($decimal)\r\n$gdb_prompt $" {
+	set main_label_offset $expect_out(1,string)
+    }
+}
+
+if { $main_length == "" || $main_label_offset == "" } {
     # Bail out here, because we can't do the following tests if
-    # $main_length is unknown.
+    # $main_length or $main_label_offset is unknown.
     return -1
 }
 
@@ -71,7 +80,7 @@ gdb_exit
 set asm_file [standard_output_file $srcfile2]
 Dwarf::assemble $asm_file {
     declare_labels partial_label int_label int_label2
-    global main_length
+    global main_length main_label_offset
 
     extern main
 
@@ -79,8 +88,8 @@ Dwarf::assemble $asm_file {
 	partial_label: partial_unit {} {
 	    subprogram {
 		{name main}
-		{low_pc main addr}
-		{high_pc "main + $main_length" addr}
+		{low_pc "main_label - $main_label_offset" addr}
+		{high_pc "main_label - $main_label_offset + $main_length" addr}
 	    }
 	}
     }
diff --git a/gdb/testsuite/gdb.dwarf2/main.c b/gdb/testsuite/gdb.dwarf2/main.c
index 3ddd194..e6d4715 100644
--- a/gdb/testsuite/gdb.dwarf2/main.c
+++ b/gdb/testsuite/gdb.dwarf2/main.c
@@ -20,5 +20,6 @@
 int
 main()
 {
+  asm ("main_label: .globl main_label");
   return 0;
 }