[PATCH 2/2] Fix implptr-optimized-out.exp fail in thumb mode

[Yao Qi <yao@codesourcery.com>]

Hi,
I see the fail in gdb.dwarf2/implptr-optimized-out.exp in thumb mode

(gdb) p p->f^M
No symbol "p" in current context.^M
(gdb) FAIL: gdb.dwarf2/implptr-optimized-out.exp: p p->f

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'.

gdb/testsuite:

2014-09-29  Yao Qi  <yao@codesourcery.com>

	* gdb.dwarf2/implptr-optimized-out.exp: Compile main.c to object.
	Calculate the offset of main_label to main.  Compile the generated
	asm file and link the executable.
	(Dwarf::assemble): Get address of main by
	main_label - $main_label_offset.
---
 gdb/testsuite/gdb.dwarf2/implptr-optimized-out.exp | 39 ++++++++++++++++++++--
 1 file changed, 36 insertions(+), 3 deletions(-)

diff --git a/gdb/testsuite/gdb.dwarf2/implptr-optimized-out.exp b/gdb/testsuite/gdb.dwarf2/implptr-optimized-out.exp
index 649f52d..534bed0 100644
--- a/gdb/testsuite/gdb.dwarf2/implptr-optimized-out.exp
+++ b/gdb/testsuite/gdb.dwarf2/implptr-optimized-out.exp
@@ -22,9 +22,35 @@ if {![dwarf2_support]} {
 standard_testfile main.c .S
 set executable ${testfile}
 
+if  {[gdb_compile ${srcdir}/${subdir}/${srcfile} ${binfile}1.o \
+	  object {}] != ""} {
+    return -1
+}
+# Start GDB and load object file, compute the offset from main to
+# main_label which are needed in the Dwarf Assembler below.
+clean_restart ${binfile}1.o
+
+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_label_offset == "" } {
+    # Bail out here, because we can't do the following tests if
+    # $main_label_offset is unknown.
+    return -1
+}
+
+gdb_exit
+
 # Create the DWARF.
 set asm_file [standard_output_file $srcfile2]
 Dwarf::assemble $asm_file {
+    global main_label_offset
+
     cu { version 3 } {
 	compile_unit {
 	    {producer "GNU C 4.4.3"}
@@ -52,8 +78,8 @@ Dwarf::assemble $asm_file {
 
 	    subprogram {
 		{name main}
-		{low_pc main addr}
-		{high_pc main+0x100 addr}
+		{low_pc "main_label - $main_label_offset" addr}
+		{high_pc "main_label - $main_label_offset + 0x100" addr}
 		{type :$int_label}
 		{external 1 flag}
 	    } {
@@ -80,10 +106,17 @@ Dwarf::assemble $asm_file {
     }
 }
 
-if [prepare_for_testing ${testfile}.exp $executable "${asm_file} ${srcfile}" {}] {
+if  {[gdb_compile $asm_file ${binfile}0.o object {}] != ""} {
     return -1
 }
 
+if  {[gdb_compile [list ${binfile}0.o ${binfile}1.o] \
+	  "${binfile}" executable {}] != ""} {
+    return -1
+}
+
+clean_restart ${testfile}
+
 # DW_OP_GNU_implicit_pointer implementation requires a valid frame.
 if ![runto_main] {
     return -1
-- 
1.9.3