[Bug libc/16881] New: gethostbyname and resolver namespace conflict

["palves at redhat dot com" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=16881

            Bug ID: 16881
           Summary: gethostbyname and resolver namespace conflict
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
          Assignee: unassigned at sourceware dot org
          Reporter: palves at redhat dot com
                CC: drepper.fsp at gmail dot com

Ref: https://sourceware.org/bugzilla/show_bug.cgi?id=16818

It seems wrong to me that calling a glibc function can mess up the
application's namespace, because the glibc function loads up libraries as an
implementation detail.  Looking around the web I find references to similar
cases of similar namespace issues.  E.g.,
http://blog.schmichael.com/2006/11/29/mdns-crashes-samba/ .  Might there be a
general solution to this issue, or do applications just need to keep working
around this by renaming their functions ?

Follows a paste of the original GDB bug report, for convenience.
---------------------------------------------------------------

"GDB generates a SIGSEGV whenever target remote hostname:port command is used
(either in .gdbinit or by command).  Tracked this down to what appears to be a
namespace conflict for timeval_add.  Stack trace inserted below.  There is a
global symbol in libsamba-util.so.0 (timeval_add) and also in libiberty which
is part of GDB.  This is version Fedora 7.6.1-46.fc19.

[fc19 gdb-7.6.1]$ readelf -s /lib64/libsamba-util.so.0 | grep timeval_add
   326: 0000003d78a0f0a0    59 FUNC    GLOBAL DEFAULT   12
timeval_add@@SAMBA_UTIL_0.0.1
[fc19 gdb-7.6.1]$ readelf -s /lib64/libsamba-util.so.0 | grep
timeval_current_ofs
   231: 0000003d78a0f130    63 FUNC    GLOBAL DEFAULT   12
timeval_current_ofs_msec@@SAMBA_UTIL_0.0.1
   343: 0000003d78a0f100    43 FUNC    GLOBAL DEFAULT   12
timeval_current_ofs@@SAMBA_UTIL_0.0.1
   691: 0000003d78a0f170    59 FUNC    GLOBAL DEFAULT   12
timeval_current_ofs_usec@@SAMBA_UTIL_0.0.1

#0  timeval_add (result=0x7fffffffd850, a=0x0, b=0x3d090) at
../../libiberty/timeval-utils.c:57
#1  0x0000003d78a0f124 in timeval_current_ofs () from /lib64/libsamba-util.so.0
#2  0x0000003d71e12b84 in name_query () from /usr/lib64/samba/libgse.so
#3  0x00007ffff0d3d489 in _nss_wins_gethostbyname_r () from
/lib64/libnss_wins.so.2
#4  0x0000003d3ad0ebd3 in gethostbyname_r@@GLIBC_2.2.5 () from /lib64/libc.so.6
During symbol reading, Child DIE 0xa7383 and its abstract origin 0xa7e56 have
different tags.
During symbol reading, Child DIE 0xa7383 and its abstract origin 0xa7e56 have
different parents.
#5  0x0000003d3ad0e316 in gethostbyname () from /lib64/libc.so.6
#6  0x000000000047d69a in net_open (scb=0xdb30d0, name=<optimized out>) at
../../gdb/ser-tcp.c:194
During symbol reading, cannot get low and high bounds for subprogram DIE at
1217621.
During symbol reading, Multiple children of DIE 0x12ba07 refer to DIE 0x129485
as their abstract origin.
During symbol reading, DW_AT_GNU_call_site_target target DIE has invalid low
pc, for referencing DIE 0x12efd3 [in module
/home/bruce/rpmbuild/BUILD/gdb-7.6.1/build-x86_64-redhat-linux/gdb/gdb].
#7  0x0000000000637f04 in serial_open (name=<optimized out>,
name@entry=0xc2219e "office:1234") at ../../gdb/serial.c:221
#8  0x00000000004a3eac in remote_serial_open (name=0xc2219e "hdev:1234") at
../../gdb/remote.c:3712
#9  remote_open_1 (name=<optimized out>, from_tty=0, target=0xb22160
<remote_ops>, extended_p=0) at ../../gdb/remote.c:4257
#10 0x000000000064127a in execute_command (p=0xc221a8 "4", p@entry=0xc22190
"target remote office:1234", from_tty=0) at ../../gdb/top.c:487
#11 0x0000000000641efb in command_loop () at ../../gdb/top.c:590
#12 0x0000000000641fb9 in read_command_file (stream=stream@entry=0xcd51a0) at
../../gdb/top.c:330
#13 0x00000000004bcc42 in script_from_file (stream=stream@entry=0xcd51a0,
file=file@entry=0xd48860 "/home/bruce/.gdbinit") at
../../gdb/cli/cli-script.c:1654
#14 0x00000000004bd366 in source_script_from_stream (stream=0xcd51a0,
file=0xd48860 "/home/bruce/.gdbinit") at ../../gdb/cli/cli-cmds.c:545
#15 0x00000000004bf04f in source_script_with_search (file=0xd48860
"/home/bruce/.gdbinit", from_tty=<optimized out>, search_path=0)
    at ../../gdb/cli/cli-cmds.c:582
#16 0x0000000000584a2e in catch_command_errors (command=0x4bf170
<source_script>, arg=0xd48860 "/home/bruce/.gdbinit",
from_tty=from_tty@entry=0, 
    mask=mask@entry=6) at ../../gdb/exceptions.c:573
#17 0x000000000058773f in captured_main (data=data@entry=0x7fffffffe010) at
../../gdb/main.c:958
#18 0x000000000058495a in catch_errors (func=func@entry=0x586430
<captured_main>, func_args=func_args@entry=0x7fffffffe010, 
    errstring=errstring@entry=0x7207cb "", mask=mask@entry=6) at
../../gdb/exceptions.c:546
#19 0x00000000005878d4 in gdb_main (args=args@entry=0x7fffffffe010) at
../../gdb/main.c:1144
#20 0x00000000004543de in main (argc=<optimized out>, argv=<optimized out>) at
../../gdb/gdb.c:34
(top-gdb)

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