[Bug c++/17772] New: libstdc++'s debug info confuses gdb (with "reproducer")

["eclig at gmx dot net" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=17772

            Bug ID: 17772
           Summary: libstdc++'s debug info confuses gdb (with
                    "reproducer")
           Product: gdb
           Version: unknown
            Status: NEW
          Severity: normal
          Priority: P2
         Component: c++
          Assignee: unassigned at sourceware dot org
          Reporter: eclig at gmx dot net

Created attachment 8035
  --> https://sourceware.org/bugzilla/attachment.cgi?id=8035&action=edit
source file demonstrating the problem

I'm having trouble displaying structure members with certain names in
GDB.  In this concrete example GDB refuses to display the member
called `complex':

    $ cat gdb-reproducer.cpp
    #include <iostream>

    using std::cout;

    typedef struct {
            int rlevel;
            int complex;
    } param_t;

    int main(int argc, char *argv[]) {
            param_t foo;

            foo.rlevel = 4;
            foo.complex= foo.rlevel + 11;

            cout << "foo.complex: " << foo.complex << "\n";

            return(0);
    }

    $ g++ -Wall -ggdb3  gdb-reproducer.cpp && ./a.out
    foo.complex: 15

    $ gdb a.out
    GNU gdb (Debian 7.7.1+dfsg-3) 7.7.1
    Copyright (C) 2014 Free Software Foundation, Inc.
    License GPLv3+: GNU GPL version 3 or later
<http://gnu.org/licenses/gpl.html>
    This is free software: you are free to change and redistribute it.
    There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
    and "show warranty" for details.
    This GDB was configured as "x86_64-linux-gnu".
    Type "show configuration" for configuration details.
    For bug reporting instructions, please see:
    <http://www.gnu.org/software/gdb/bugs/>.
    Find the GDB manual and other documentation resources online at:
    <http://www.gnu.org/software/gdb/documentation/>.
    For help, type "help".
    Type "apropos word" to search for commands related to "word"...
    Reading symbols from a.out...done.
    (gdb) b main
    Breakpoint 1 at 0x4007c6: file gdb-reproducer.cpp, line 13.
    (gdb) r
    Starting program: /home/lopes/projects/c/a.out

    Breakpoint 1, main (argc=1, argv=0x7fffffffe958) at gdb-reproducer.cpp:13
    13        foo.rlevel = 4;
    (gdb) n
    14        foo.complex= foo.rlevel + 11;
    (gdb) n
    16        cout << "foo.complex: " << foo.complex << "\n";
    (gdb) p foo
    $1 = {rlevel = 4, complex = 15}
    (gdb) ptype foo
    type = struct param_t {
        int rlevel;
        int complex;
    }
    (gdb) p foo.complex
    A syntax error in expression, near `'.


Trying to find the culprit I came upon this:

    (gdb) info shared
    From                To                  Syms Read   Shared Object Library
    0x00007ffff7ddcae0  0x00007ffff7df5170  Yes        
/lib64/ld-linux-x86-64.so.2
                                            No          linux-vdso.so.1
    0x00007ffff7b2c8e0  0x00007ffff7b9480a  Yes        
/usr/lib/x86_64-linux-gnu/libstdc++.so.6
    0x00007ffff77d5580  0x00007ffff7840de6  Yes        
/lib/x86_64-linux-gnu/libm.so.6
    0x00007ffff75bcab0  0x00007ffff75cc995  Yes        
/lib/x86_64-linux-gnu/libgcc_s.so.1
    0x00007ffff72304a0  0x00007ffff735a613  Yes        
/lib/x86_64-linux-gnu/libc.so.6
    (gdb) noshared
    (gdb) p foo.complex
    $2 = 15
    (gdb) p foo
    $3 = {rlevel = 4, complex = 15}
    (gdb) p foo.complex
    $4 = 15
    (gdb) shared libstdc.*
    Reading symbols from
/usr/lib/x86_64-linux-gnu/libstdc++.so.6...Reading symbols from
/usr/lib/debug//usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.20...done.
    done.
    Loaded symbols for /usr/lib/x86_64-linux-gnu/libstdc++.so.6
    (gdb) p foo.complex
    A syntax error in expression, near `'.
    (gdb) p foo
    $5 = {rlevel = 4, complex = 15}
    (gdb) ptype foo
    type = struct param_t {
        int rlevel;
        int complex;
    }

This suggests that something in the debug info of libstdc++ seems to
be causing the problem.

Some info about the system I'm using:

    $ uname -a
    Linux lopes 3.14-1-amd64 #1 SMP Debian 3.14.12-1 (2014-07-11) x86_64
GNU/Linux
    $ g++ -v
    Using built-in specs.
    COLLECT_GCC=g++
    COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.9/lto-wrapper
    Target: x86_64-linux-gnu
    Configured with: ../src/configure -v --with-pkgversion='Debian 4.9.1-4'
--with-bugurl=file:///usr/share/doc/gcc-4.9/README.Bugs
--enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.9 --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.9 --libdir=/usr/lib --enable-nls
--with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --enable-gnu-unique-object --disable-vtable-verify
--enable-plugin --with-system-zlib --disable-browser-plugin
--enable-java-awt=gtk --enable-gtk-cairo
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64/jre --enable-java-home
--with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.9-amd64
--with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar
--enable-objc-gc --enable-multiarch --with-arch-32=i586 --with-abi=m64
--with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic
--enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
--target=x86_64-linux-gnu
    Thread model: posix
    gcc version 4.9.1 (Debian 4.9.1-4)
    $ dpkg -l | grep -F 'libstdc++'
    ii  libstdc++-4.9-dev:amd64 4.9.1-4          amd64            GNU Standard
C++ Library v3 (development files)
    ii  libstdc++6:amd64        4.9.1-4          amd64            GNU Standard
C++ Library v3
    ii  libstdc++6-4.9-dbg:amd6 4.9.1-4          amd64            GNU Standard
C++ Library v3 (debugging files)
    $ dpkg -l | grep -F 'gcc'
    ii  gcc                     4:4.9.0-4        amd64            GNU C
compiler
    ii  gcc-4.7-base:amd64      4.7.4-2          amd64            GCC, the GNU
Compiler Collection (base package)
    ii  gcc-4.8                 4.8.3-7          amd64            GNU C
compiler
    ii  gcc-4.8-base:amd64      4.8.3-7          amd64            GCC, the GNU
Compiler Collection (base package)
    ii  gcc-4.9                 4.9.1-4          amd64            GNU C
compiler
    ii  gcc-4.9-base:amd64      4.9.1-4          amd64            GCC, the GNU
Compiler Collection (base package)
    ii  libgcc-4.8-dev:amd64    4.8.3-7          amd64            GCC support
library (development files)
    ii  libgcc-4.9-dev:amd64    4.9.1-4          amd64            GCC support
library (development files)
    ii  libgcc1:amd64           1:4.9.1-4        amd64            GCC support
library
    ii  libgcc1-dbg:amd64       1:4.9.1-4        amd64            GCC support
library (debug symbols)
    ii  linux-compiler-gcc-4.8- 3.14.15-2        amd64            Compiler for
Linux on x86 (meta-package)

Please let me know if you can reproduce this.  I've also seen this
error when using GDB 7.8 and IIRC 7.6.

I'm working on somewhat larger codebase, with lots of automatically
generated code from XML files, using those structures.  So I would be
very thankful if someone could provide a workaround (aside from
abstaining from a debugging-enabled libstdc++) or a patch for this
"interesting behaviour".

Thank you very much!

 EmÃlio

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