https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81077
Bug ID: 81077
Summary: linker constants are randomized
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: gregory.mounie at imag dot fr
Target Milestone: ---
Created attachment 41540
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=41540&action=edit
printf of two linker constants using & and [] notations
When compiling with linker constants, the constants values does not have the
given values but looks randomized. They change values at each execution.
Theses constants have really only an address but no values. The symbol table of
the executable is still correct according to objdump.
Code of my test file (testld.c (the .i file is in attachment)
#include <stdio.h>
extern unsigned char liloo;
extern unsigned char lilootab[];
static void * spa = & liloo;
static void * sta = lilootab;
int main() {
void * pa = & liloo;
void * ta = lilootab;
printf("%p %p %p %p\n", spa, sta, pa, ta);
return 0;
}
Command line of compilation:
gcc -v -save-temps -Wl,--defsym=liloo=0x1000000 -Wl,--defsym=lilootab=0x2000000
testld.c -o testld
Output of the compilation:
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/6/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 6.3.0-18'
--with-bugurl=file:///usr/share/doc/gcc-6/README.Bugs
--enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-6 --program-prefix=x86_64-linux-gnu- --enable-shared
--enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext
--enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/
--enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes
--with-default-libstdcxx-abi=new --enable-gnu-unique-object
--disable-vtable-verify --enable-libmpx --enable-plugin --enable-default-pie
--with-system-zlib --disable-browser-plugin --enable-java-awt=gtk
--enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-6-amd64/jre
--enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-6-amd64
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-6-amd64
--with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar
--with-target-system-zlib --enable-objc-gc=auto --enable-multiarch
--with-arch-32=i686 --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 6.3.0 20170516 (Debian 6.3.0-18)
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-o' 'testld' '-mtune=generic'
'-march=x86-64'
/usr/lib/gcc/x86_64-linux-gnu/6/cc1 -E -quiet -v -imultiarch x86_64-linux-gnu
testld.c -mtune=generic -march=x86-64 -fpch-preprocess -o testld.i
ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
ignoring nonexistent directory
"/usr/lib/gcc/x86_64-linux-gnu/6/../../../../x86_64-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
/usr/lib/gcc/x86_64-linux-gnu/6/include
/usr/local/include
/usr/lib/gcc/x86_64-linux-gnu/6/include-fixed
/usr/include/x86_64-linux-gnu
/usr/include
End of search list.
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-o' 'testld' '-mtune=generic'
'-march=x86-64'
/usr/lib/gcc/x86_64-linux-gnu/6/cc1 -fpreprocessed testld.i -quiet -dumpbase
testld.c -mtune=generic -march=x86-64 -auxbase testld -version -o testld.s
GNU C11 (Debian 6.3.0-18) version 6.3.0 20170516 (x86_64-linux-gnu)
compiled by GNU C version 6.3.0 20170516, GMP version 6.1.2, MPFR
version 3.1.5, MPC version 1.0.3, isl version 0.15
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
GNU C11 (Debian 6.3.0-18) version 6.3.0 20170516 (x86_64-linux-gnu)
compiled by GNU C version 6.3.0 20170516, GMP version 6.1.2, MPFR
version 3.1.5, MPC version 1.0.3, isl version 0.15
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: 0fe3e671dc62e01e15c40cc5df58cb5f
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-o' 'testld' '-mtune=generic'
'-march=x86-64'
as -v --64 -o testld.o testld.s
Version de l'assembleur GNU 2.28 (x86_64-linux-gnu) utilisant la version BFD
(GNU Binutils for Debian) 2.28
COMPILER_PATH=/usr/lib/gcc/x86_64-linux-gnu/6/:/usr/lib/gcc/x86_64-linux-gnu/6/:/usr/lib/gcc/x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/6/:/usr/lib/gcc/x86_64-linux-gnu/
LIBRARY_PATH=/usr/lib/gcc/x86_64-linux-gnu/6/:/usr/lib/gcc/x86_64-linux-gnu/6/../../../x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/6/../../../../lib/:/lib/x86_64-linux-gnu/:/lib/../lib/:/usr/lib/x86_64-linux-gnu/:/usr/lib/../lib/:/usr/lib/gcc/x86_64-linux-gnu/6/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-o' 'testld' '-mtune=generic'
'-march=x86-64'
/usr/lib/gcc/x86_64-linux-gnu/6/collect2 -plugin
/usr/lib/gcc/x86_64-linux-gnu/6/liblto_plugin.so
-plugin-opt=/usr/lib/gcc/x86_64-linux-gnu/6/lto-wrapper
-plugin-opt=-fresolution=testld.res -plugin-opt=-pass-through=-lgcc
-plugin-opt=-pass-through=-lgcc_s -plugin-opt=-pass-through=-lc
-plugin-opt=-pass-through=-lgcc -plugin-opt=-pass-through=-lgcc_s --sysroot=/
--build-id --eh-frame-hdr -m elf_x86_64 --hash-style=gnu -dynamic-linker
/lib64/ld-linux-x86-64.so.2 -pie -o testld
/usr/lib/gcc/x86_64-linux-gnu/6/../../../x86_64-linux-gnu/Scrt1.o
/usr/lib/gcc/x86_64-linux-gnu/6/../../../x86_64-linux-gnu/crti.o
/usr/lib/gcc/x86_64-linux-gnu/6/crtbeginS.o -L/usr/lib/gcc/x86_64-linux-gnu/6
-L/usr/lib/gcc/x86_64-linux-gnu/6/../../../x86_64-linux-gnu
-L/usr/lib/gcc/x86_64-linux-gnu/6/../../../../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/6/../../.. --defsym=liloo=0x1000000
--defsym=lilootab=0x2000000 testld.o -lgcc --as-needed -lgcc_s --no-as-needed
-lc -lgcc --as-needed -lgcc_s --no-as-needed
/usr/lib/gcc/x86_64-linux-gnu/6/crtendS.o
/usr/lib/gcc/x86_64-linux-gnu/6/../../../x86_64-linux-gnu/crtn.o
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-o' 'testld' '-mtune=generic'
'-march=x86-64'
Output (Correct) of: objdump -t testld | grep liloo
0000000002000000 g *ABS* 0000000000000000 lilootab
0000000001000000 g *ABS* 0000000000000000 liloo
Output of two successive executions (Incorrect):
./testld
0x555f85bb7000 0x555f86bb7000 0x555f85bb7000 0x555f86bb7000
./testld
0x5572284b4000 0x5572294b4000 0x5572284b4000 0x5572294b4000
Output using gcc-5 compiler (gcc-5 (Debian 5.4.1-11) 5.4.1 20170519 )
./testld-5
0x1000000 0x2000000 0x1000000 0x2000000
Gcc version (in Debian) producing executable with correct output:
gcc-4.8.5, 4.9.4, 5.4.1
(for reference clang 3.{6,7,8,9},4.0,5.0 are working too)
Additional Gcc version (Debian) failing to produce executable with correct
output
gcc-7 -v
Using built-in specs.
COLLECT_GCC=gcc-7
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/7/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 7.1.0-6'
--with-bugurl=file:///usr/share/doc/gcc-7/README.Bugs
--enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++ --prefix=/usr
--with-gcc-major-version-only --program-suffix=-7
--program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes
--with-default-libstdcxx-abi=new --enable-gnu-unique-object
--disable-vtable-verify --enable-libmpx --enable-plugin --enable-default-pie
--with-system-zlib --with-target-system-zlib --enable-objc-gc=auto
--enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64
--with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic
--enable-offload-targets=nvptx-none --without-cuda-driver
--enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
--target=x86_64-linux-gnu
Thread model: posix
gcc version 7.1.1 20170522 (Debian 7.1.0-6)
