https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71033
Bug ID: 71033 Summary: Segmentation fault c + intel assembly, unable to use EBX 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 38459 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=38459&action=edit the 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) 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. Used makefile: CC=gcc CFLAGS= -Wall -m32 -O0 -save-temps 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 command : make && ./fun 2 f.o: f.s nasm -f elf -g f.s -o f.o main.c : #include "f.h" //only void f(char*) int main(int argc, char *argv[]) { if(argc < 2) { return 1; } f(argv[1]); return 0; } f.s : ;f.i is not generated section .text global f f: push ebp mov ebp, esp mov eax, [ebp+8] mov ebx, 9 begin: mov cl, [eax] cmp cl, 0 jz end add cl, 1 mov [eax], cl inc eax jmp begin end: mov esp, ebp pop ebp ret