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What is a good way to debug stack value corruption. In a program of mine sometimes the address of the this pointer gets changed after a method returns that does a shutdown on a file descriptor. I debugged the program for hours but I can not find the problem.
What is a good method to find out what changes the address of the this pointer? When I manually add a watch on the this pointer the error would not occur. The error still occurs when I strip down my code as much as possible. I tried Valgrind but it does not find any early stack corruption.
I managed to detect when the error occurs, I compiled the code in 64 bit mode. The address of this changed from 0xxxxxxx to 0x1000000xxxxxxx. I check the address of this in the methods where the error occurs, that I found out when the address changes (see the first paragraaf for this).
Is there any other way to find out the cause of this problem?
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When a stack corruption is detected, one should look at the local variables in the called and calling functions to look for possible sources of memory corruption. Check array and pointer declarations for sources of errors. Sometimes stray corruption of a processors registers might also be due to a stack corruption.
Compiling with --fstack-protector-all will cause your program to abort (with signal SIGABRT) when it returns from a function that corrupts the stack, if that corruption includes the area of the stack around the return address.
In general, Valgrind detection of overflows in stack and global variables is weak to non-existant. Arguably, Valgrind is the wrong tool for that job. If you are on one of supported platforms, building with -fmudflap and linking with -lmudflap will give you much better results for these kinds of errors.
You might want to give a shot to address-sanitizer. It is available in gcc 4.8:
AddressSanitizer , a fast memory error detector, has been added and can be enabled via
-fsanitize=address. Memory access instructions will be instrumented to detect heap-, stack-, and global-buffer overflow as well as use-after-free bugs. To get nicer stacktraces, use-fno-omit-frame-pointer. The AddressSanitizer is available on IA-32/x86-64/x32/PowerPC/PowerPC64 GNU/Linux and on x86-64 Darwin.
In GCC (but apparently not clang), you need to specify -fsanitize=address in both the compiler flags and linker flags, as described in this related answer.
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