Hi! On Sat, Jun 29, 2019 at 07:53:36PM +0000, Mahmood Naderan via gcc-help wrote: > An empty main code results in the following opcode and assembly lines according to GDB. > > $ gcc -masm=intel -g test.c -o test Use -S to see the actual assembler code generated: $ gcc -masm=intel -S test.c and look at the generated test.s file. > I expected to see something like this > > > 0x00000000004004ed <+0>: 55 push rbp > 0x00000000004004ee <+1>: 48 89 e5 mov rbp,rsp > ==========> 00 INVALID > 0x00000000004004f1 <+4>: 5d pop rbp > 0x00000000004004f2 <+5>: c3 ret 00 is not an invalid opcode. It is the start of an "add" instruction, as GDB showed you. > Can I do that? You could use 0xcc which is a single-byte instruction that breaks your program (it's "int3"). It isn't clear what you actually want to do though? Segher
