[patch] Regressed TLS variables type (PR 13448)

[Jan Kratochvil <jan dot kratochvil at redhat dot com>]

Hi,

http://sourceware.org/bugzilla/show_bug.cgi?id=13448
FAIL:
	(gdb) print myname
	$2 = 1936287860
PASS:
	(gdb) print myname
	$4 = "this is the main thread", '\000' <repeats 104 times>


9602d20e52e1a2291bd9edbdf98e4d82995a385e is the first bad commit
[RFA] Nullified garbage-collected global variables
http://sourceware.org/ml/gdb-patches/2010-07/msg00206.html
commit 9602d20e52e1a2291bd9edbdf98e4d82995a385e
Author: Jerome Guitton <guitton@adacore.com>
Date:   Mon Jul 26 09:29:59 2010 +0000
    gdb/
	* dwarf2read.c (add_partial_symbol): Do not add a global variable if
	its adress is null. Add comment to explain why.
	(new_symbol): Ditto.

Added a testcase for the patch of Jul 2010 causing the regression.
Added a fix and a testcase for the regressed case.

The fix is not great, it further hacks up decode_locdesc, which I already
replaced before but later returned back by the revertion:
	[patch#2] fetch result of locdesc expressions as integer (not address)
	http://sourceware.org/ml/gdb-patches/2011-10/msg00225.html

After archer-jankratochvil-vla or its equivalent gets merged it may be fixed
better, at least the testcase exists for it now.

I will check it in in a day or so.  It is a "recent" regression.

No regressions on {x86_64,x86_64-m32,i686}-fedora16-linux-gnu.


Thanks,
Jan


gdb/
2011-12-01  Jan Kratochvil  <jan.kratochvil@redhat.com>

	PR 13448
	* dwarf2read.c (decode_locdesc): Handle DW_OP_const8u.
	For DW_OP_GNU_push_tls_address increment the value, new comment for it.

gdb/testsuite/
2011-12-01  Jan Kratochvil  <jan.kratochvil@redhat.com>

	PR 13448
	* gdb.dwarf2/dw2-var-zero-addr.S:: New file.
	* gdb.dwarf2/dw2-var-zero-addr.exp:: New file.
	* gdb.threads/tls-var-main.c:: New file.
	* gdb.threads/tls-var.c:: New file.
	* gdb.threads/tls-var.exp:: New file.

--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -14667,6 +14667,11 @@ decode_locdesc (struct dwarf_block *blk, struct dwarf2_cu *cu)
 	  i += 4;
 	  break;
 
+	case DW_OP_const8u:
+	  stack[++stacki] = read_8_bytes (objfile->obfd, &data[i]);
+	  i += 8;
+	  break;
+
 	case DW_OP_constu:
 	  stack[++stacki] = read_unsigned_leb128 (NULL, (data + i),
 						  &bytes_read);
@@ -14714,9 +14719,12 @@ decode_locdesc (struct dwarf_block *blk, struct dwarf2_cu *cu)
 	  /* Nothing should follow this operator, so the top of stack would
 	     be returned.  */
 	  /* This is valid for partial global symbols, but the variable's
-	     address will be bogus in the psymtab.  */
+	     address will be bogus in the psymtab.  Make it always at least
+	     non-zero to not look as a variable garbage collected by linker
+	     which have DW_OP_addr 0.  */
 	  if (i < size)
 	    dwarf2_complex_location_expr_complaint ();
+	  stack[stacki]++;
           break;
 
 	case DW_OP_GNU_uninit:
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-var-zero-addr.S
@@ -0,0 +1,92 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2011 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+	.data
+
+	.section .debug_info
+.Lcu1_begin:
+	/* CU header */
+	.4byte	.Lcu1_end - .Lcu1_start		/* Length of Compilation Unit */
+.Lcu1_start:
+	.2byte	2				/* DWARF Version */
+	.4byte	.Labbrev1_begin			/* Offset into abbrev section */
+	.byte	4				/* Pointer size */
+
+	/* CU die */
+	.uleb128 1				/* Abbrev: DW_TAG_compile_unit */
+	.ascii	"dw2-var-zero-addr.c\0"		/* DW_AT_name */
+	.ascii	"GNU C 4.3.2\0"			/* DW_AT_producer */
+	.byte	1				/* DW_AT_language (C) */
+
+.Ltype_uchar:
+	.uleb128	2			/* Abbrev: DW_TAG_base_type */
+	.ascii		"int\0"			/* DW_AT_name */
+	.byte		4			/* DW_AT_byte_size */
+	.byte		5			/* DW_AT_encoding */
+
+	.uleb128	3			/* Abbrev: DW_TAG_variable (location) */
+	.ascii		"var\0"			/* DW_AT_name */
+	.byte		2f - 1f			/* DW_AT_location */
+1:	.byte		3			/*   DW_OP_addr */
+	.4byte		0			/*   <addr> */
+2:	.4byte		.Ltype_uchar-.Lcu1_begin	/* DW_AT_type */
+
+	.byte		0			/* End of children of CU */
+
+.Lcu1_end:
+
+/* Abbrev table */
+	.section .debug_abbrev
+.Labbrev1_begin:
+	.uleb128	1			/* Abbrev code */
+	.uleb128	0x11			/* DW_TAG_compile_unit */
+	.byte		1			/* has_children */
+	.uleb128	0x3			/* DW_AT_name */
+	.uleb128	0x8			/* DW_FORM_string */
+	.uleb128	0x25			/* DW_AT_producer */
+	.uleb128	0x8			/* DW_FORM_string */
+	.uleb128	0x13			/* DW_AT_language */
+	.uleb128	0xb			/* DW_FORM_data1 */
+	.byte		0x0			/* Terminator */
+	.byte		0x0			/* Terminator */
+
+	.uleb128	2			/* Abbrev code */
+	.uleb128	0x24			/* DW_TAG_base_type */
+	.byte		0			/* has_children */
+	.uleb128	0x3			/* DW_AT_name */
+	.uleb128	0x8			/* DW_FORM_string */
+	.uleb128	0xb			/* DW_AT_byte_size */
+	.uleb128	0xb			/* DW_FORM_data1 */
+	.uleb128	0x3e			/* DW_AT_encoding */
+	.uleb128	0xb			/* DW_FORM_data1 */
+	.byte		0x0			/* Terminator */
+	.byte		0x0			/* Terminator */
+
+	.uleb128	3			/* Abbrev code (location) */
+	.uleb128	0x34			/* DW_TAG_variable */
+	.byte		0			/* has_children */
+	.uleb128	0x3			/* DW_AT_name */
+	.uleb128	0x8			/* DW_FORM_string */
+	.uleb128	0x2			/* DW_AT_location */
+	.uleb128	0xa			/* DW_FORM_block1 */
+	.uleb128	0x49			/* DW_AT_type */
+	.uleb128	0x13			/* DW_FORM_ref4 */
+	.byte		0x0			/* Terminator */
+	.byte		0x0			/* Terminator */
+
+	.byte		0x0			/* Terminator */
+	.byte		0x0			/* Terminator */
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-var-zero-addr.exp
@@ -0,0 +1,29 @@
+# Copyright 2011 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if {![dwarf2_support]} {
+    return 0  
+}
+
+set testfile dw2-var-zero-addr
+if [prepare_for_testing ${testfile}.exp ${testfile} [list ${testfile}.S main.c] {nodebug}] {
+    return -1
+}
+
+# FAIL was: = (int *) 0x0
+# Such DIE record can be produced using: gcc -fdata-sections -Wl,-gc-sections
+gdb_test "print &var" {No symbol "var" in current context\.}
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/tls-var-main.c
@@ -0,0 +1,22 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2011 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+int
+main (void)
+{
+  return 0;
+}
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/tls-var.c
@@ -0,0 +1,23 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2011 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <pthread.h>
+
+/* Place this variable to a separate CU (Compilation Unit) from main so that it
+   has delayed full symtab expansion.  */
+
+__thread const char *tls_var = "hello";
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/tls-var.exp
@@ -0,0 +1,40 @@
+# Copyright 2011 Free Software Foundation, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+set testfile tls-var
+set srcfile ${testfile}.c
+set srcmainfile ${testfile}-main.c
+set objfile ${objdir}/${subdir}/${testfile}.o
+set objmainfile ${objdir}/${subdir}/${testfile}-main.o
+set executable ${testfile}
+set binfile ${objdir}/${subdir}/${executable}
+
+if { [gdb_compile ${srcdir}/${subdir}/${srcfile} ${objfile} object {debug}] != ""
+     || [gdb_compile ${srcdir}/${subdir}/${srcmainfile} ${objmainfile} object {}] != ""
+     || [gdb_compile_pthreads "${objfile} ${objmainfile}" ${binfile} executable {}] != ""} {
+    return -1
+}
+
+clean_restart ${executable}
+
+if ![runto_main] {
+    return 0
+}
+
+# FAIL was: type = <thread local variable, no debug info>
+gdb_test "whatis tls_var" {type = const char \*}
+
+# FAIL was: $1 = 4195832
+gdb_test "print tls_var" { = 0x[0-9a-f]+ "hello"}