https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71030
Bug ID: 71030
Summary: Strange segmentation fault
Product: gcc
Version: 6.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: formateu at gmail dot com
Target Milestone: ---
Created attachment 38457
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=38457&action=edit
preprocessed file
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-linux-gnu/6.1.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /build/gcc-multilib/src/gcc/configure --prefix=/usr
--libdir=/usr/lib --libexecdir=/usr/lib --mandir=/usr/share/man
--infodir=/usr/share/info --with-bugurl=https://bugs.archlinux.org/
--enable-languages=c,c++,ada,fortran,go,lto,objc,obj-c++ --enable-shared
--enable-threads=posix --enable-libmpx --with-system-zlib --with-isl
--enable-__cxa_atexit --disable-libunwind-exceptions --enable-clocale=gnu
--disable-libstdcxx-pch --disable-libssp --enable-gnu-unique-object
--enable-linker-build-id --enable-lto --enable-plugin
--enable-install-libiberty --with-linker-hash-style=gnu
--enable-gnu-indirect-function --enable-multilib --disable-werror
--enable-checking=release
Thread model: posix
gcc version 6.1.1 20160501 (GCC)
Used makefile
CC=gcc
CFLAGS= -Wall -m32
all: main.o f.o
$(CC) $(CFLAGS) main.o f.o -o fun
main.o: main.c
$(CC) $(CFLAGS) -c main.c -o main.o
f.o: f.s
nasm -f elf -g f.s -o f.o
make && ./fun 2 2
Program runs intel x86 assembly function in main. Use of the EBX register
inside that function causes segmentation fault (after return from function).
It seems like gcc is using EBX instead of EBP before function call.
Program compiled using clang works properly.
Bug was noticed firstly on gcc 5.3.0 version, but is still present on latest
repository version.
main.c file :
#include "f.h" // only void f(int); + guardian
int main()
{
int var = 4;
f(var);
return 0;
}
f.s file :
section .text
global f
f:
push ebp
mov ebp, esp
mov eax, [ebp+8]
mov ebx, 0
begin:
mov cl, [eax]
mov ebx, 0
add cl, 1
mov [eax], cl
mov esp, ebp
pop ebp
ret
