Re: [RFA/dwarf] Anonymous nested function causes SEGV during psymbol read

[Joel Brobecker <brobecker at adacore dot com>]

> Thanks again for the feedback.  Attached is a new version of the patch,
> with the complaints added.  Since I also added a complaint for the
> non-nested case, I also extended the testcase to cover that case as
> well.

Yet another version: Instead of generating the complaint while creating
the psymbols, I decided to generate them during the symtab creation
phase. A couple of reasons:
  - From an implementation perspective, it means that I only have to
    generate the complete from one location in our code.
  - Instead of generating a complaint for all broken DIEs all at once
    at startup, just generate them when it affects a unit which the user
    is actually referring to.
  - If we ever get rid of the psymtab, we'd lose the warning...

That's why I like this version better...

-- 
Joel

commit 82a94c19a204c46c5666e72a9071bf99d481a275
Author: Joel Brobecker <brobecker@adacore.com>
Date:   Wed Feb 17 07:29:04 2010 +0400

    [dwarf] Anonymous nested function causes SEGV during psymbol read
    
    According to the DWARF3 standard, a function always has a name attribute
    (Section 3.3 - Subroutine and Entry Point Entries).  The only exception
    is when a DW_AT_abstract_origin attribute is provided, in which case
    the name may be inherited from the referenced DIE.
    
    The problem occured because our compiler generated a subprogram DIE
    for a nested function where the name attribute was missing (and no
    abstract-origin either).  Our code in add_partial_symbol is not
    prepared to deal with the situation, and happily just tries  to compute
    the length of the (NULL) function name.
    
    This normally cannot happen, because there is already a guard in
    scan_partial_symbols, where we (silently!) ignore anonymous dies,
    including anonymous subprograms. Unfortunately, there is a flaw that
    affects Ada and other languages that allow nested subprograms. For
    nested subprograms, we do not go through scan_partial_symbols and
    thus we are missing the name check.
    
    This patch adds the name check in the nested subprogram case. It also
    adds a complaint which is emitted during the psymtab->symtab conversion
    phase.
    
    gdb/ChangeLog:
    
            * dwarf2read.c (add_partial_subprogram): Make sure the subprogram
            DIE has a name before creating the associated partial symbol.
            (read_func_scope): Emit a complaint if the subprogram does not
            have a name or when we can't extract the subprogram PC bounds.
    
    gdb/testsuite/ChangeLog:
    
            * gdb.dwarf2/dw2-anonymous-func.S: New file.
            * gdb.dwarf2/dw2-anonymous-func.exp: New testcase.
    
    Tested on x86_64-linux, no regression.  Note that the testcase also
    verifies that the psymtab->symtab conversion does not crash (this is
    the purpose of the "list file1.txt:1" test.

diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index 563cb18..02b10d9 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -2573,7 +2573,11 @@ add_partial_subprogram (struct partial_die_info *pdi,
 				 cu->per_cu->psymtab);
 	    }
           if (!pdi->is_declaration)
-            add_partial_symbol (pdi, cu);
+	    /* Ignore subprogram DIEs that do not have a name, they are
+	       illegal.  Do not emit a complaint at this point, we will
+	       do so when we convert this psymtab into a symtab.  */
+	    if (pdi->name)
+	      add_partial_symbol (pdi, cu);
         }
     }
   
@@ -3857,10 +3861,23 @@ read_func_scope (struct die_info *die, struct dwarf2_cu *cu)
 
   name = dwarf2_name (die, cu);
 
-  /* Ignore functions with missing or empty names and functions with
-     missing or invalid low and high pc attributes.  */
-  if (name == NULL || !dwarf2_get_pc_bounds (die, &lowpc, &highpc, cu, NULL))
-    return;
+  /* Ignore functions with missing or empty names.  These are actually
+     illegal according to the DWARF standard.  */
+  if (name == NULL)
+    {
+      complaint (&symfile_complaints,
+                 _("missing name for subprogram DIE at %d"), die->offset);
+      return;
+    }
+
+  /* Ignore functions with missing or invalid low and high pc attributes.  */
+  if (!dwarf2_get_pc_bounds (die, &lowpc, &highpc, cu, NULL))
+    {
+      complaint (&symfile_complaints,
+                 _("cannot get low and high bounds for subprogram DIE at %d"),
+                 die->offset);
+      return;
+    }
 
   lowpc += baseaddr;
   highpc += baseaddr;
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-anonymous-func.S b/gdb/testsuite/gdb.dwarf2/dw2-anonymous-func.S
new file mode 100644
index 0000000..84552bf
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-anonymous-func.S
@@ -0,0 +1,248 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2004, 2007, 2008, 2009, 2010 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/>.  */
+
+/* Test a minimal file containing DWARF-2 information.  This test also
+   serves as a skeleton for other DWARF-2 tests.  Most other tests will
+   not be this extensively itemized and commented...  */
+
+/* Dummy function to provide debug information for.  */
+
+	.text
+.Lbegin_text1:
+	.globl func_cu1
+	.type func_cu1, %function
+func_cu1:
+.Lbegin_func_cu1:
+	.int 0
+.Lend_func_cu1:
+	.size func_cu1, .-func_cu1
+	.globl func_cu2
+	.type func_cu2, %function
+func_cu2:
+.Lbegin_func_cu2:
+	.int 0
+.Lend_func_cu2:
+	.size func_cu2, .-func_cu2
+.Lend_text1:
+
+/* Debug information */
+
+	.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 */
+	.4byte	.Lline1_begin			/* DW_AT_stmt_list */
+	.4byte	.Lend_text1			/* DW_AT_high_pc */
+	.4byte	.Lbegin_text1			/* DW_AT_low_pc */
+	.ascii	"file1.txt\0"			/* DW_AT_name */
+	.ascii	"GNU C 3.3.3\0"			/* DW_AT_producer */
+	.byte	0x0d				/* DW_AT_language (Ada95) */
+
+	/* func_cu1 */
+	.uleb128	2			/* Abbrev: DW_TAG_subprogram */
+	.byte		1			/* DW_AT_external */
+	.byte		1			/* DW_AT_decl_file */
+	.byte		2			/* DW_AT_decl_line */
+	.ascii		"func_cu1\0"		/* DW_AT_name */
+	.4byte		.Ltype_int-.Lcu1_begin	/* DW_AT_type */
+	.4byte		.Lbegin_func_cu1	/* DW_AT_low_pc */
+	.4byte		.Lend_func_cu1		/* DW_AT_high_pc */
+	.byte		1			/* DW_AT_frame_base: length */
+	.byte		0x55			/* DW_AT_frame_base: DW_OP_reg5 */
+	/* Nested function missing a name attribute.  */
+	.uleb128	4			/* Abbrev: DW_TAG_subprogram */
+	.byte		1			/* DW_AT_external */
+	.byte		1			/* DW_AT_decl_file */
+	.byte		2			/* DW_AT_decl_line */
+	.4byte		.Ltype_int-.Lcu1_begin	/* DW_AT_type */
+	.4byte		.Lbegin_func_cu2	/* DW_AT_low_pc */
+	.4byte		.Lend_func_cu2		/* DW_AT_high_pc */
+	.byte		1			/* DW_AT_frame_base: length */
+	.byte		0x55			/* DW_AT_frame_base: DW_OP_reg5 */
+	.byte		0x0			/* End of children of func_cu1 */
+
+	/* Non-nested function missing a name attribute.  */
+	.uleb128	4			/* Abbrev: DW_TAG_subprogram */
+	.byte		1			/* DW_AT_external */
+	.byte		1			/* DW_AT_decl_file */
+	.byte		2			/* DW_AT_decl_line */
+	.4byte		.Ltype_int-.Lcu1_begin	/* DW_AT_type */
+	.4byte		.Lbegin_func_cu2	/* DW_AT_low_pc */
+	.4byte		.Lend_func_cu2		/* DW_AT_high_pc */
+	.byte		1			/* DW_AT_frame_base: length */
+	.byte		0x55			/* DW_AT_frame_base: DW_OP_reg5 */
+
+.Ltype_int:
+	.uleb128	3			/* Abbrev: DW_TAG_base_type */
+	.ascii		"int\0"			/* DW_AT_name */
+	.byte		4			/* DW_AT_byte_size */
+	.byte		5			/* DW_AT_encoding */
+
+	.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	0x10			/* DW_AT_stmt_list */
+	.uleb128	0x6			/* DW_FORM_data4 */
+	.uleb128	0x12			/* DW_AT_high_pc */
+	.uleb128	0x1			/* DW_FORM_addr */
+	.uleb128	0x11			/* DW_AT_low_pc */
+	.uleb128	0x1			/* DW_FORM_addr */
+	.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	0x2e			/* DW_TAG_subprogram */
+	.byte		1			/* has_children */
+	.uleb128	0x3f			/* DW_AT_external */
+	.uleb128	0xc			/* DW_FORM_flag */
+	.uleb128	0x3a			/* DW_AT_decl_file */
+	.uleb128	0xb			/* DW_FORM_data1 */
+	.uleb128	0x3b			/* DW_AT_decl_line */
+	.uleb128	0xb			/* DW_FORM_data1 */
+	.uleb128	0x3			/* DW_AT_name */
+	.uleb128	0x8			/* DW_FORM_string */
+	.uleb128	0x49			/* DW_AT_type */
+	.uleb128	0x13			/* DW_FORM_ref4 */
+	.uleb128	0x11			/* DW_AT_low_pc */
+	.uleb128	0x1			/* DW_FORM_addr */
+	.uleb128	0x12			/* DW_AT_high_pc */
+	.uleb128	0x1			/* DW_FORM_addr */
+	.uleb128	0x40			/* DW_AT_frame_base */
+	.uleb128	0xa			/* DW_FORM_block1 */
+	.byte		0x0			/* Terminator */
+	.byte		0x0			/* Terminator */
+
+	.uleb128	3			/* 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	4			/* Abbrev code */
+	.uleb128	0x2e			/* DW_TAG_subprogram */
+	.byte		0			/* has_children */
+	.uleb128	0x3f			/* DW_AT_external */
+	.uleb128	0xc			/* DW_FORM_flag */
+	.uleb128	0x3a			/* DW_AT_decl_file */
+	.uleb128	0xb			/* DW_FORM_data1 */
+	.uleb128	0x3b			/* DW_AT_decl_line */
+	.uleb128	0xb			/* DW_FORM_data1 */
+	.uleb128	0x49			/* DW_AT_type */
+	.uleb128	0x13			/* DW_FORM_ref4 */
+	.uleb128	0x11			/* DW_AT_low_pc */
+	.uleb128	0x1			/* DW_FORM_addr */
+	.uleb128	0x12			/* DW_AT_high_pc */
+	.uleb128	0x1			/* DW_FORM_addr */
+	.uleb128	0x40			/* DW_AT_frame_base */
+	.uleb128	0xa			/* DW_FORM_block1 */
+	.byte		0x0			/* Terminator */
+	.byte		0x0			/* Terminator */
+
+	.byte		0x0			/* Terminator */
+	.byte		0x0			/* Terminator */
+
+/* Line table */
+	.section .debug_line
+.Lline1_begin:
+	.4byte		.Lline1_end - .Lline1_start	/* Initial length */
+.Lline1_start:
+	.2byte		2			/* Version */
+	.4byte		.Lline1_lines - .Lline1_hdr	/* header_length */
+.Lline1_hdr:
+	.byte		1			/* Minimum insn length */
+	.byte		1			/* default_is_stmt */
+	.byte		1			/* line_base */
+	.byte		1			/* line_range */
+	.byte		0x10			/* opcode_base */
+
+	/* Standard lengths */
+	.byte		0
+	.byte		1
+	.byte		1
+	.byte		1
+	.byte		1
+	.byte		0
+	.byte		0
+	.byte		0
+	.byte		1
+	.byte		0
+	.byte		0
+	.byte		1
+	.byte		0
+	.byte		0
+	.byte		0
+
+	/* Include directories */
+	.byte		0
+
+	/* File names */
+	.ascii		"file1.txt\0"
+	.uleb128	0
+	.uleb128	0
+	.uleb128	0
+
+	.byte		0
+
+.Lline1_lines:
+	.byte		0	/* DW_LNE_set_address */
+	.uleb128	5
+	.byte		2
+	.4byte		.Lbegin_func_cu1
+
+	.byte		3	/* DW_LNS_advance_line */
+	.sleb128	3	/* ... to 4 */
+
+	.byte		1	/* DW_LNS_copy */
+
+	.byte		1	/* DW_LNS_copy (second time as an end-of-prologue marker) */
+
+	.byte		0	/* DW_LNE_set_address */
+	.uleb128	5
+	.byte		2
+	.4byte		.Lend_func_cu1
+
+	.byte		0	/* DW_LNE_end_of_sequence */
+	.uleb128	1
+	.byte		1
+
+.Lline1_end:
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-anonymous-func.exp b/gdb/testsuite/gdb.dwarf2/dw2-anonymous-func.exp
new file mode 100644
index 0000000..10662eb
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-anonymous-func.exp
@@ -0,0 +1,53 @@
+# Copyright 2004, 2005, 2007, 2008, 2009, 2010 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/>.
+
+# Minimal DWARF-2 unit test
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+# For now pick a sampling of likely targets.
+if {![istarget *-*-linux*]
+    && ![istarget *-*-gnu*]
+    && ![istarget *-*-elf*]
+    && ![istarget *-*-openbsd*]
+    && ![istarget arm-*-eabi*]
+    && ![istarget powerpc-*-eabi*]} {
+    return 0
+}
+
+set testfile "dw2-anonymous-func"
+set dwarf_srcfile "file1.txt"
+set srcfile ${testfile}.S
+set binfile ${objdir}/${subdir}/${testfile}.x
+
+if  { [gdb_compile "${srcdir}/${subdir}/main.c" "main.o" object {debug}] != "" } {
+    return -1
+}
+
+if  { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${testfile}.o" object {nodebug}] != "" } {
+    return -1
+}
+
+if  { [gdb_compile "${testfile}.o main.o" "${binfile}" executable {debug}] != "" } {
+    return -1
+}
+
+gdb_exit
+gdb_start
+gdb_reinitialize_dir $srcdir/$subdir
+gdb_load ${binfile}
+
+# Force the debugger to create the file1.txt symtab, to make sure that
+# the debugger does not crash doing so.
+gdb_test "list file1.txt:1" "File 1 Line 1.*File 1 Line 8" "list file1.txt"