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[PATCH] Regression setting breakpoint


There is a regression when setting a breakpoint which was introduced
in gdb-7.3 by a fix in this patch:
https://sourceware.org/ml/gdb-patches/2010-03/msg00220.html

The regression shows up in C when the linkage name is different
from the internal symbol name.  For example,

   void goo (int b) asm("_goo");
   void goo (int b) {}

will create a function with the linkage name of "_goo" and the DWARF
will describe the source name of "goo".  There is both a DW_AT_name and
DW_AT_linkage_name in the DIE for this function.  Some compilers
(e.g., ICC) have options allowing linkage names to have characters
prepended to the source name so that the linkage name is different
from the source name and can not be computed from it.

Prior to this patch, a breakpoint at "_goo" would find the linkage
symbol, and one at "goo" would find the source symbol.  After the
patch, the source name is replace with the linkage name.

The attached patch fixes this by making die_needs_namespace()
return 0 for any C language program.  There's also a test case.

I'm not sure that this is the right fix for the problem, although
I'm pretty sure that it should not break anything.  There is code
in dwarf2_compute_name() which only calls die_needs_namespace()
for C++, Java, or Fortran programs, which could be moved into
die_needs_namespace().  Possibly the fix should be in dwarf2_physname()
where the call to die_needs_namespace() is done before the check for
DW_AT_linkage_name is done.

Comment:  Much of the code in dwarf2_compute_name(), dwarf2_physname(),
and related functions seems complex, convoluted, and confusing (the
big Three C's).  The source name for a symbol is not the same as
the fully qualified name and it's not the same as the linkage name.
That a language supports FQNs with namespaces does not seem to me
to say that this should have anything to do with what the linkage (aka
physical) name for the symbol is.

--
Michael Eager	 eager@eagercon.com
1960 Park Blvd., Palo Alto, CA 94306  650-325-8077
>From 6e6a7110f950e3d90978637b21fcb913934be9b1 Mon Sep 17 00:00:00 2001
From: Michael Eager <eager@eagercon.com>
Date: Tue, 10 Dec 2013 11:50:27 -0800
Subject: [PATCH] Fix regression symbol name different from linkage name.

gdb:
*  dwarf2read.c (die_needs_namespace): Do nothing for C language.

testsuite:
*  gdb.base/break-linker-symname.c: New.
*  gdb.base/break-linker-symname.exp: New.
---
 gdb/dwarf2read.c                                |    3 ++
 gdb/testsuite/gdb.base/break-linker-symname.c   |   28 +++++++++++++++++++++++
 gdb/testsuite/gdb.base/break-linker-symname.exp |   25 ++++++++++++++++++++
 3 files changed, 56 insertions(+), 0 deletions(-)
 create mode 100644 gdb/testsuite/gdb.base/break-linker-symname.c
 create mode 100644 gdb/testsuite/gdb.base/break-linker-symname.exp

diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index 3974d0b..d2a236c 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -8044,6 +8044,9 @@ die_needs_namespace (struct die_info *die, struct dwarf2_cu *cu)
 {
   struct attribute *attr;
 
+  if (cu->language == language_c)
+    return 0;
+
   switch (die->tag)
     {
     case DW_TAG_namespace:
diff --git a/gdb/testsuite/gdb.base/break-linker-symname.c b/gdb/testsuite/gdb.base/break-linker-symname.c
new file mode 100644
index 0000000..8728ea1
--- /dev/null
+++ b/gdb/testsuite/gdb.base/break-linker-symname.c
@@ -0,0 +1,28 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2013 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/>.  */
+
+void goo (int b) asm("_goo");
+
+void goo (int b) 
+{
+} 
+
+int main (void)
+{
+  goo (4);
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.base/break-linker-symname.exp b/gdb/testsuite/gdb.base/break-linker-symname.exp
new file mode 100644
index 0000000..2a86f37
--- /dev/null
+++ b/gdb/testsuite/gdb.base/break-linker-symname.exp
@@ -0,0 +1,25 @@
+#   Copyright 2013 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 that 'set breakpoint always-inserted 1' is not a brick
+# Also verifies that breakpoint enabling/disabling works properly
+# with duplicated breakpoints.
+
+if { [prepare_for_testing break-linker-symname.exp break-linker-symname break-linker-symname.c] } {
+    return -1
+}
+
+gdb_test "break _goo" "Breakpoint 1.*" "set breakpoint on linker symbol"
+gdb_test "break goo" "Breakpoint 2.*" "set breakpoint on source symbol"
-- 
1.7.1


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