Hey I wonder if we can solve this using your thought on making it compiler agnostic, by having lldb use a "step out" rather than a "step" at that point? I would hope the debugger can manage to step out of the function doing that approach regardless of the "number of steps" it would take to do it with a gcc vs. clang exe.
Just a thought. That would avoid needing separate paths for gcc and clang. Otherwise, it for sure seems like the current test flow would need to change based on compiler. I like going with the first approach, if that's valid, so we can avoid having (say) yet another compiler do something else which requires yet a different path. -Todd On Tue, Jul 22, 2014 at 5:30 PM, Doug Snyder <[email protected]> wrote: > > the test case “test_step_over_with_dwarf_python” for unit test > "functionalities/step-avoids-no debug” passes when compiling the unit test > with clang and fails when compiling with gcc, when i run the unit test in > linux (ubuntu 14.04). note: to run this test case in linux, you have to > comment out the “@skipIfLinux # intermittent failure” line. > > the failure happens when the python code in TestStepNoDebug.py does the > first self.thread.StepOut() after the breakpoint. > > this appears to be caused by gcc generating significantly different code > than clang. clang associates 20 bytes of machine code (all of the machine > code related to the source line) to the breakpoint source line (line 12), > but gcc only associates the first 3 bytes of machine code to line 12. gcc > associates the remaining bytes related to line 12 with line 13. the > corresponding code for both versions is shown at the bottom of this email. > > this difference means that when the self.thread.StepOut() is executed in > the clang version, the program steps to the source line of the calling > routine (line 19), but the gcc version steps to the next source line (line > 13). this mismatch causes TestStepNoDebug.py to report a failure not > really caused by lldb, but really just a compiler difference. > > it seems like the tests in TestStepNoDebug.py should be rewritten to > include different tests for clang and gcc, or the test should be > restructured to not rely on compiler differences - at least not clang and > gcc differences. > > > > shown below is the objdump for the clang version. the 20 bytes from > 40055c thru 40056f (inclusive) are associated with source line 12 (no bytes > are associated with source line 13). > > int > called_from_nodebug_actual(int some_value) > { > 400530: 55 push %rbp > 400531: 48 89 e5 mov %rsp,%rbp > 400534: 48 83 ec 10 sub $0x10,%rsp > 400538: 48 b8 d4 06 40 00 00 movabs $0x4006d4,%rax > 40053f: 00 00 00 > 400542: 89 7d fc mov %edi,-0x4(%rbp) > int return_value = 0; > 400545: c7 45 f8 00 00 00 00 movl $0x0,-0x8(%rbp) > return_value = printf ("Length: %d.\n", some_value); > 40054c: 8b 75 fc mov -0x4(%rbp),%esi > 40054f: 48 89 c7 mov %rax,%rdi > 400552: b0 00 mov $0x0,%al > 400554: e8 b7 fe ff ff callq 400410 <printf@plt> > 400559: 89 45 f8 mov %eax,-0x8(%rbp) > return return_value; // Stop here and step out of me > 40055c: 8b 45 f8 mov -0x8(%rbp),%eax > 40055f: 48 83 c4 10 add $0x10,%rsp > 400563: 5d pop %rbp > 400564: c3 retq > 400565: 66 66 2e 0f 1f 84 00 data32 nopw %cs:0x0(%rax,%rax,1) > 40056c: 00 00 00 00 > > 0000000000400570 <called_from_nodebug>: > } > > > > shown below is the objdump for the gcc version. the 3 bytes from 400556 > thru 400558 (inclusive) are associated with source line 12, and the 2 bytes > from 400559 thru 40055a (inclusive) are associated with source line 13. > > called_from_nodebug_actual(int some_value) > { > 40052d: 55 push %rbp > 40052e: 48 89 e5 mov %rsp,%rbp > 400531: 48 83 ec 20 sub $0x20,%rsp > 400535: 89 7d ec mov %edi,-0x14(%rbp) > int return_value = 0; > 400538: c7 45 fc 00 00 00 00 movl $0x0,-0x4(%rbp) > return_value = printf ("Length: %d.\n", some_value); > 40053f: 8b 45 ec mov -0x14(%rbp),%eax > 400542: 89 c6 mov %eax,%esi > 400544: bf 94 06 40 00 mov $0x400694,%edi > 400549: b8 00 00 00 00 mov $0x0,%eax > 40054e: e8 bd fe ff ff callq 400410 <printf@plt> > 400553: 89 45 fc mov %eax,-0x4(%rbp) > return return_value; // Stop here and step out of me > 400556: 8b 45 fc mov -0x4(%rbp),%eax > } > 400559: c9 leaveq > 40055a: c3 retq > > 000000000040055b <called_from_nodebug>: > > > doug > > > _______________________________________________ > lldb-dev mailing list > [email protected] > http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev > > -- Todd Fiala | Software Engineer | [email protected] | 650-943-3180
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