egcs/libc interaction (resend)
Robert Krawitz
rlk@torrent.com
Tue Oct 6 14:57:00 GMT 1998
[I never got any confirmation on this, and never received a copy back]
This seems to be an interaction between egcs 1.1, libc5 (5.4.46,
dynload 1.9.9, binutils 2.9.1.0.7, but it happened with other binutils
versions). I don't have g++ 2.7.2 handy, but this problem didn't seem
to happen when we were using g++ (perhaps we just didn't see it). It
also doesn't happen on libc6.
It looks like even though I've called fpclose on the appropriate FILE
pointer, the I/O code is still caching it, and getting into trouble
when the shared libraries go away.
.PHONY: test2
CFLAGS= -O -fPIC
test2:
g++ $(CFLAGS) -c test1.C
g++ $(CFLAGS) -c test2.C
g++ $(CFLAGS) -c test3.C
g++ $(CFLAGS) -shared test1.o -o test1.so
g++ $(CFLAGS) -shared test3.o -o test3.so
g++ $(CFLAGS) -v -Wl,--verbose -o test2 test2.o test1.so -ldl
% make
g++ -O -fPIC -c test1.C
g++ -O -fPIC -c test2.C
g++ -O -fPIC -c test3.C
g++ -O -fPIC -shared test1.o -o test1.so
g++ -O -fPIC -shared test3.o -o test3.so
g++ -O -fPIC -v -Wl,--verbose -o test2 test2.o test1.so -ldl
Reading specs from /usr/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.91.57/specs
gcc version egcs-2.91.57 19980901 (egcs-1.1 release)
/usr/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.91.57/collect2 -m elf_i386 -dynamic-linker /lib/ld-linux.so.1 -o test2 /usr/lib/crt1.o /usr/lib/crti.o /usr/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.91.57/crtbegin.o -L/usr/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.91.57 -L/usr/i686-pc-linux-gnulibc1/lib --verbose test2.o test1.so -ldl -lstdc++ -lm -lgcc -lc -lgcc /usr/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.91.57/crtend.o /usr/lib/crtn.o
GNU ld version 2.9.1 (with BFD 2.9.1.0.7)
Supported emulations:
elf_i386
i386linux
i386coff
using internal linker script:
==================================================
OUTPUT_FORMAT("elf32-i386", "elf32-i386",
"elf32-i386")
OUTPUT_ARCH(i386)
ENTRY(_start)
SEARCH_DIR(/lib); SEARCH_DIR(/usr/lib); SEARCH_DIR(/usr/local/lib); SEARCH_DIR(/usr/i586-unknown-linux-gnulibc1/lib);
/* Do we need any of these for elf?
__DYNAMIC = 0; */
SECTIONS
{
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. = 0x08048000 + SIZEOF_HEADERS;
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.rel.text :
{ *(.rel.text) *(.rel.gnu.linkonce.t*) }
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{ *(.rela.text) *(.rela.gnu.linkonce.t*) }
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{ *(.rel.data) *(.rel.gnu.linkonce.d*) }
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.rel.rodata :
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.init : { *(.init) } =0x9090
.plt : { *(.plt) }
.text :
{
*(.text)
*(.stub)
/* .gnu.warning sections are handled specially by elf32.em. */
*(.gnu.warning)
*(.gnu.linkonce.t*)
} =0x9090
_etext = .;
PROVIDE (etext = .);
.fini : { *(.fini) } =0x9090
.rodata : { *(.rodata) *(.gnu.linkonce.r*) }
.rodata1 : { *(.rodata1) }
/* Adjust the address for the data segment. We want to adjust up to
the same address within the page on the next page up. */
. = ALIGN(0x1000) + (. & (0x1000 - 1));
.data :
{
*(.data)
*(.gnu.linkonce.d*)
CONSTRUCTORS
}
.data1 : { *(.data1) }
.ctors :
{
*(.ctors)
}
.dtors :
{
*(.dtors)
}
.got : { *(.got.plt) *(.got) }
.dynamic : { *(.dynamic) }
/* We want the small data sections together, so single-instruction offsets
can access them all, and initialized data all before uninitialized, so
we can shorten the on-disk segment size. */
.sdata : { *(.sdata) }
_edata = .;
PROVIDE (edata = .);
__bss_start = .;
.sbss : { *(.sbss) *(.scommon) }
.bss :
{
*(.dynbss)
*(.bss)
*(COMMON)
}
. = ALIGN(32 / 8);
_end = . ;
PROVIDE (end = .);
/* Stabs debugging sections. */
.stab 0 : { *(.stab) }
.stabstr 0 : { *(.stabstr) }
.stab.excl 0 : { *(.stab.excl) }
.stab.exclstr 0 : { *(.stab.exclstr) }
.stab.index 0 : { *(.stab.index) }
.stab.indexstr 0 : { *(.stab.indexstr) }
.comment 0 : { *(.comment) }
/* DWARF debug sections.
Symbols in the DWARF debugging sections are relative to the beginning
of the section so we begin them at 0. */
/* DWARF 1 */
.debug 0 : { *(.debug) }
.line 0 : { *(.line) }
/* GNU DWARF 1 extensions */
.debug_srcinfo 0 : { *(.debug_srcinfo) }
.debug_sfnames 0 : { *(.debug_sfnames) }
/* DWARF 1.1 and DWARF 2 */
.debug_aranges 0 : { *(.debug_aranges) }
.debug_pubnames 0 : { *(.debug_pubnames) }
/* DWARF 2 */
.debug_info 0 : { *(.debug_info) }
.debug_abbrev 0 : { *(.debug_abbrev) }
.debug_line 0 : { *(.debug_line) }
.debug_frame 0 : { *(.debug_frame) }
.debug_str 0 : { *(.debug_str) }
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.debug_macinfo 0 : { *(.debug_macinfo) }
/* SGI/MIPS DWARF 2 extensions */
.debug_weaknames 0 : { *(.debug_weaknames) }
.debug_funcnames 0 : { *(.debug_funcnames) }
.debug_typenames 0 : { *(.debug_typenames) }
.debug_varnames 0 : { *(.debug_varnames) }
/* These must appear regardless of . */
}
==================================================
attempt to open /usr/lib/crt1.o succeeded
/usr/lib/crt1.o
attempt to open /usr/lib/crti.o succeeded
/usr/lib/crti.o
attempt to open /usr/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.91.57/crtbegin.o succeeded
/usr/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.91.57/crtbegin.o
attempt to open test2.o succeeded
test2.o
attempt to open test1.so succeeded
test1.so
attempt to open /usr/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.91.57/libdl.so failed
attempt to open /usr/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.91.57/libdl.a failed
attempt to open /usr/i686-pc-linux-gnulibc1/lib/libdl.so failed
attempt to open /usr/i686-pc-linux-gnulibc1/lib/libdl.a failed
attempt to open /opt/gnu/bin/../lib/libdl.so failed
attempt to open /opt/gnu/bin/../lib/libdl.a failed
attempt to open /lib/libdl.so succeeded
-ldl (/lib/libdl.so)
attempt to open /usr/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.91.57/libstdc++.so failed
attempt to open /usr/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.91.57/libstdc++.a failed
attempt to open /usr/i686-pc-linux-gnulibc1/lib/libstdc++.so failed
attempt to open /usr/i686-pc-linux-gnulibc1/lib/libstdc++.a failed
attempt to open /opt/gnu/bin/../lib/libstdc++.so failed
attempt to open /opt/gnu/bin/../lib/libstdc++.a succeeded
attempt to open /usr/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.91.57/libm.so failed
attempt to open /usr/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.91.57/libm.a failed
attempt to open /usr/i686-pc-linux-gnulibc1/lib/libm.so failed
attempt to open /usr/i686-pc-linux-gnulibc1/lib/libm.a failed
attempt to open /opt/gnu/bin/../lib/libm.so succeeded
-lm (/opt/gnu/bin/../lib/libm.so)
attempt to open /usr/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.91.57/libgcc.so failed
attempt to open /usr/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.91.57/libgcc.a succeeded
attempt to open /usr/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.91.57/libc.so failed
attempt to open /usr/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.91.57/libc.a failed
attempt to open /usr/i686-pc-linux-gnulibc1/lib/libc.so failed
attempt to open /usr/i686-pc-linux-gnulibc1/lib/libc.a failed
attempt to open /opt/gnu/bin/../lib/libc.so succeeded
-lc (/opt/gnu/bin/../lib/libc.so)
attempt to open /usr/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.91.57/libgcc.so failed
attempt to open /usr/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.91.57/libgcc.a succeeded
attempt to open /usr/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.91.57/crtend.o succeeded
/usr/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.91.57/crtend.o
attempt to open /usr/lib/crtn.o succeeded
/usr/lib/crtn.o
test.h:
class base
{
public:
base();
virtual ~base();
virtual void doFile();
static base *allocate(const char *name);
virtual int registerBaseClass();
protected:
void doRegistration(const char *className, base * (*allocatefcn)(void));
private:
struct registry
{
char *typename_;
base *(*allocatefcn_)(void);
struct registry *next_;
};
static struct registry *sTheRegistry_;
};
void loadDerived();
void unloadDerived();
test1.C:
#include <iostream.h>
#include <dlfcn.h>
#include <unistd.h>
#include <string.h>
#include "test.h"
struct base::registry *base::sTheRegistry_ = 0;
base::base()
{
cerr << "Construct base at " << (void *) this << endl;
}
base::~base()
{
cerr << "Destroy base at " << (void *) this << endl;
}
void
base::doFile()
{
cerr << "base::doFile" << endl;
}
static base *
allocateBase()
{
return new base;
}
static base sTheBase;
int
base::registerBaseClass()
{
doRegistration("base", &allocateBase);
return 0;
}
static int regDummy = sTheBase.registerBaseClass();
base *
base::allocate(const char *name)
{
registry *t = sTheRegistry_;
while (t)
{
if (!strcmp(name, t->typename_))
return (t->allocatefcn_)();
t = t->next_;
}
return 0;
}
void
base::doRegistration(const char *className, base * (*allocatefcn)())
{
registry *tmp = new registry;
tmp->typename_ = new char[strlen(className) + 1];
strcpy(tmp->typename_, className);
tmp->allocatefcn_ = allocatefcn;
tmp->next_ = base::sTheRegistry_;
base::sTheRegistry_ = tmp;
}
void *derivedHandle;
void
loadDerived()
{
char buffer[2048];
if (!getcwd(buffer, 2047))
{
cerr << "Unable to get cwd" << endl;
exit(1);
}
strcat(buffer, "/test3.so");
if ((derivedHandle = dlopen(buffer, RTLD_NOW | RTLD_GLOBAL)) != 0)
return;
cerr << dlerror() << endl;
exit(2);
}
void
unloadDerived()
{
char buffer[2048];
if (!getcwd(buffer, 2047))
{
cerr << "Unable to get cwd" << endl;
exit(1);
}
strcat(buffer, "/test3.so");
if (dlclose(derivedHandle) == 0)
return;
cerr << dlerror() << endl;
exit(2);
}
test3.C:
#include <iostream.h>
#include "test.h"
#include <stdio.h>
class derived : public base
{
public:
derived();
virtual ~derived();
virtual void doFile();
virtual int registerDerivedClass();
};
derived::derived()
{
cerr << "Construct derived at " << (void *) this << endl;
}
derived::~derived()
{
cerr << "Destroy derived at " << (void *) this << endl;
}
void
derived::doFile()
{
FILE *out_fp = fopen("/tmp/broken", "w");
if (!out_fp)
{
cerr << "Unable to open /tmp/broken" << endl;
return;
}
fprintf(out_fp, "Here I am\n");
fclose(out_fp);
}
static base *
allocateDerived()
{
return new derived;
}
static derived sTheDerived;
int
derived::registerDerivedClass()
{
doRegistration("derived", &allocateDerived);
return 0;
}
static int regDummy = sTheDerived.registerDerivedClass();
test2.C:
#include <string.h>
#include <iostream.h>
#include "test.h"
int debug = 0;
int
main(int, char **)
{
base *theBase = base::allocate("base");
theBase->doFile();
delete theBase;
loadDerived();
base *theDerived = base::allocate("derived");
theDerived->doFile();
delete theDerived;
unloadDerived();
return 0;
}
--
Robert Krawitz <rlk@torrent.com> Founding Engineer
Torrent Systems Inc. 617-354-8484x104
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