[committed][gdb/testsuite] Fix gdb.dlang/watch-loc.exp on ppc64

[Tom de Vries]

Hi,

On ppc64, we run into:
...
/tmp/ccKXURmw.s: Assembler messages:^M
/tmp/ccKXURmw.s:99: Error: can't resolve \
  `_Dmain_end' {.text section} - `_Dmain' {.opd section}^M
compiler exited with status 1
...

The unresolvable entity comes from the .debug_aranges section hardcoded in
watch-loc.c:
...
"      .4byte  _Dmain \n"      // Address
"      .4byte  _Dmain_end - _Dmain \n" // Length
...
where _Dmain is the function label for function _Dmain, and _Dmain_end is a
label after function _Dmain:
...
int _Dmain (void)
{
  asm ("_Dmain_label: .globl _Dmain_label");
  return 0;
}

asm ("_Dmain_end: .globl _Dmain_end");
...

The problem is that the two labels are not in the same section, because _Dmain
ends up in the .opd section, which "contains the official procedure
descriptors.  A pointer to a function shall reference a procedure descriptor in
this section."

Fix this by using function_range instead to get the length.

Also, fix the address part to not use _Dmain, but instead use the function
start as returned by function_range.

Tested on x86_64-linux.

Committed to trunk.

Thanks,
- Tom

[gdb/testsuite] Fix gdb.dlang/watch-loc.exp on ppc64

gdb/testsuite/ChangeLog:

2020-09-16  Tom de Vries  <tdevries@suse.de>

	PR testsuite/26617
	* gdb.dlang/watch-loc.c: Only add .debug_aranges if
        WITH_DEBUG_SECTIONS is defined.
	(xstr, str): New macro.
	(.debug_aranges): Use DMAIN_START_0/1/2 and DMAIN_LENGTH
	to get start and size of _Dmain.
	* gdb.dlang/watch-loc.exp: Pass DMAIN_START_0/1/2 and DMAIN_LENGTH
	using additional_flags.

---
 gdb/testsuite/gdb.dlang/watch-loc.c   |  8 ++++++--
 gdb/testsuite/gdb.dlang/watch-loc.exp | 17 ++++++++++++++++-
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/gdb/testsuite/gdb.dlang/watch-loc.c b/gdb/testsuite/gdb.dlang/watch-loc.c
index de594f35ae..0a58f27d9f 100644
--- a/gdb/testsuite/gdb.dlang/watch-loc.c
+++ b/gdb/testsuite/gdb.dlang/watch-loc.c
@@ -36,6 +36,9 @@ main (void)
   return _Dmain ();
 }
 
+#ifdef WITH_DEBUG_SECTIONS
+#define xstr(s) str(s)
+#define str(s) #s
 /* The .debug_names-based index support depends on .debug_aranges
    generated by GCC.  (.gdb_index includes a gdb-generated map
    instead.)  */
@@ -52,10 +55,11 @@ asm (
 "	.byte	0 \n"	// Size of Segment Descriptor
 "	.2byte	0 \n"	// Pad to 16 byte boundary
 "	.2byte	0 \n"
-"	.4byte	_Dmain \n"	// Address
-"	.4byte	_Dmain_end - _Dmain \n"	// Length
+"	.4byte	" xstr(DMAIN_START_0) xstr(DMAIN_START_1) xstr(DMAIN_START_2) "\n"		// Address
+"	.4byte	" xstr(DMAIN_LENGTH) "\n"	// Length
 "	.4byte	0 \n"
 "	.4byte	0 \n"
 ".Laranges_end: \n"
 "	.popsection \n"
 );
+#endif
diff --git a/gdb/testsuite/gdb.dlang/watch-loc.exp b/gdb/testsuite/gdb.dlang/watch-loc.exp
index d65f3c674f..dcd93789ce 100644
--- a/gdb/testsuite/gdb.dlang/watch-loc.exp
+++ b/gdb/testsuite/gdb.dlang/watch-loc.exp
@@ -27,6 +27,10 @@ if {![dwarf2_support]} {
 
 standard_testfile watch-loc.c watch-loc-dw.S
 
+lassign [function_range _Dmain ${srcdir}/${subdir}/${srcfile}] \
+    dmain_start dmain_length
+
+
 # Make some DWARF for the test.
 set asm_file [standard_output_file $srcfile2]
 Dwarf::assemble $asm_file {
@@ -62,8 +66,19 @@ Dwarf::assemble $asm_file {
     }
 }
 
+set dmain_start_list [split $dmain_start]
+set dmain_start_0 [lindex $dmain_start_list 0]
+set dmain_start_1 [lindex $dmain_start_list 1]
+set dmain_start_2 [lindex $dmain_start_list 2]
+
 if { [prepare_for_testing "failed to prepare" ${testfile} \
-          [list $srcfile $asm_file] {nodebug}] } {
+          [list $srcfile $asm_file] \
+	  "nodebug \
+	       additional_flags=-DWITH_DEBUG_SECTIONS \
+	       additional_flags=-DDMAIN_START_0=$dmain_start_0 \
+	       additional_flags=-DDMAIN_START_1=$dmain_start_1 \
+	       additional_flags=-DDMAIN_START_2=$dmain_start_2 \
+	       additional_flags=-DDMAIN_LENGTH=$dmain_length"] } {
     return -1
 }