[Bug gold/14330] New: failure to link global hidden symbol

[wingo at pobox dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14330

             Bug #: 14330
           Summary: failure to link global hidden symbol
           Product: binutils
           Version: 2.22
            Status: NEW
          Severity: normal
          Priority: P2
         Component: gold
        AssignedTo: address@hidden
        ReportedBy: address@hidden
                CC: address@hidden
    Classification: Unclassified


When compiling JavaScriptCore in some configurations, we get a link error.  I
believe this is due to a bug in gold.  I know it might sound far-fetched, but
it is my only explanation.

The situation is a bit complicated.  The symbol in question
(getHostCallReturnValue) is defined in assembler, and is hidden with .hidden. 
There is a public declaration for the symbol, as a function.  Like this:

HostCallReturnValue.h:

extern "C" EncodedJSValue getHostCallReturnValue()  __attribute__((used))
__attribute__((visibility("hidden")));

DFGOperations.cpp:

asm (
".globl getHostCallReturnValue\n"
".hidden getHostCallReturnValue\n"
"getHostCallReturnValue:\n"
    "mov -40(%r13), %r13\n"
    "mov %r13, %rdi\n"
    "jmp getHostCallReturnValueWithExecState\n"
);

LLIntSlowPaths.cpp has a reinterpret_cast<void*>(getHostCallReturnValue).  It
is this reference that is failing to relocate.

The strange thing is, the build usually works.  However if you build it with
CPPFLAGS=-DENABLE_DFG_JIT=0 (effectively disabling some code, but neither the
use nor the definition of getHostCallReturnValue are affected) *and* -g, then I
get the error:

g++  -fPIC -DPIC -shared -nostdlib [...] \
  Source/JavaScriptCore/dfg/.libs/libjavascriptcoregtk_3_0_la-DFGOperations.o \
  [...] \
 
Source/JavaScriptCore/llint/.libs/libjavascriptcoregtk_3_0_la-LLIntSlowPaths.o 
\
  -Wl,--whole-archive ./.libs/libWTF.a -Wl,--no-whole-archive 
-L/home/wingo/src/WebKit/WebKitBuild/Dependencies/Root/lib64 -lpthread
-licui18n -licuuc -licudata -lgmodule-2.0 -lgthread-2.0 -lrt -lgio-2.0
-lgobject-2.0 -lglib-2.0 -L/usr/lib/gcc/x86_64-linux-gnu/4.7
-L/usr/lib/gcc/x86_64-linux-gnu/4.7/../../../x86_64-linux-gnu
-L/usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../lib -L/lib/x86_64-linux-gnu
-L/lib/../lib -L/usr/lib/x86_64-linux-gnu -L/usr/lib/../lib
-L/usr/lib/gcc/x86_64-linux-gnu/4.7/../../.. -lstdc++ -lm -lc -lgcc_s
/usr/lib/gcc/x86_64-linux-gnu/4.7/crtendS.o
/usr/lib/gcc/x86_64-linux-gnu/4.7/../../../x86_64-linux-gnu/crtn.o  -O3
-pthread -O0 -Wl,--export-dynamic -pthread   -pthread -Wl,-soname
-Wl,libjavascriptcoregtk-3.0.so.0 -o .libs/libjavascriptcoregtk-3.0.so.0.13.3


/usr/bin/ld: error:
Source/JavaScriptCore/llint/.libs/libjavascriptcoregtk_3_0_la-LLIntSlowPaths.o:
requires dynamic R_X86_64_PC32 reloc against 'getHostCallReturnValue' which may
overflow at runtime; recompile with -fPIC
../../Source/JavaScriptCore/llint/LLIntSlowPaths.cpp:1302: warning: relocation
refers to discarded section
/usr/bin/ld: error: hidden symbol 'getHostCallReturnValue' is not defined
locally
../../Source/JavaScriptCore/llint/LLIntSlowPaths.cpp:1325: warning: relocation
refers to discarded section
/usr/bin/ld: error: hidden symbol 'getHostCallReturnValue' is not defined
locally
../../Source/JavaScriptCore/llint/LLIntSlowPaths.cpp:1456: warning: relocation
refers to discarded section
/usr/bin/ld: error: hidden symbol 'getHostCallReturnValue' is not defined
locally
collect2: error: ld returned 1 exit status

I have elided a number of the .o files.  I will paste a full command line as an
attachment.

Now, clearly the symbol is defined:

$ readelf -a
WebKitBuild/Debug/Source/JavaScriptCore/dfg/.libs/libjavascriptcoregtk_3_0_la-DFGOperations.o
| grep getHostCallReturnValue
000000000032  010200000002 R_X86_64_PC32     0000000000000030
getHostCallReturnValue - 4
   257: 000000000000002a     0 NOTYPE  GLOBAL HIDDEN    32
getHostCallReturnValue
   258: 0000000000000030    74 FUNC    GLOBAL HIDDEN    12
getHostCallReturnValueWit

Also the uses are clear:

$ readelf -a
WebKitBuild/Debug/Source/JavaScriptCore/llint/.libs/libjavascriptcoregtk_3_0_la-LLIntSlowPaths.o
 | grep getHostCall
00000000b87d  0d3f00000002 R_X86_64_PC32     0000000000000000
getHostCallReturnValue - 4
00000000bb6e  0d3f00000002 R_X86_64_PC32     0000000000000000
getHostCallReturnValue - 4
00000000c23e  0d3f00000002 R_X86_64_PC32     0000000000000000
getHostCallReturnValue - 4
  3391: 0000000000000000     0 NOTYPE  GLOBAL HIDDEN   UND
getHostCallReturnValue

The Debug build has some extra code paths, and is build -g -O0.  The Release
build, while differing in the extra code paths and just -O3, shows the same
definitions and uses, but does succeed in linking, without runtime text
relocations:

$ readelf -a
WebKitBuild/Release/Source/JavaScriptCore/dfg/.libs/libjavascriptcoregtk_3_0_la-DFGOperations.o
| grep getHostCallReturnValue
000000000008  000900000002 R_X86_64_PC32     0000000000000010
getHostCallReturnValue - 4
     8: 0000000000000000     0 NOTYPE  GLOBAL HIDDEN     1
getHostCallReturnValue
     9: 0000000000000010    27 FUNC    GLOBAL HIDDEN     1
getHostCallReturnValueWit
$ readelf -a
WebKitBuild/Release/Source/JavaScriptCore/llint/.libs/libjavascriptcoregtk_3_0_la-LLIntSlowPaths.o
 | grep getHostCall
00000000010e  004c00000002 R_X86_64_PC32     0000000000000000
getHostCallReturnValue - 4
00000000c395  004c00000002 R_X86_64_PC32     0000000000000000
getHostCallReturnValue - 4
    76: 0000000000000000     0 NOTYPE  GLOBAL HIDDEN   UND
getHostCallReturnValue
$ readelf -a WebKitBuild/Release/.libs/libjavascriptcoregtk-3.0.so | grep
getHostCall
  2034: 0000000000119f60     0 NOTYPE  LOCAL  HIDDEN    13
getHostCallReturnValue
  2035: 0000000000119f70    27 FUNC    LOCAL  HIDDEN    13
getHostCallReturnValueWit
$ readelf -a WebKitBuild/Release/.libs/libjavascriptcoregtk-3.0.so | grep PC32
$

I can only conclude that gold is not doing its job correctly.  What do you
think?

I apologize for not attaching a test case, but the cases in which this bug hits
are sufficiently strange that I don't know how to reduce it.  However you can
reproduce it directly if you check out WebKit from git, then:


  CPPFLAGS='-DENABLE_DFG_JIT=0' Tools/Scripts/build-jsc --gtk --debug


$ gcc --version
gcc (Debian 4.7.1-2) 4.7.1
Copyright (C) 2012 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ ld --version
GNU gold (GNU Binutils for Debian 2.22) 1.11
Copyright 2011 Free Software Foundation, Inc.
This program is free software; you may redistribute it under the terms of
the GNU General Public License version 3 or (at your option) a later version.
This program has absolutely no warranty.

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