https://bugs.kde.org/show_bug.cgi?id=398445
--- Comment #8 from Stas Sergeev <s...@list.ru> --- (In reply to Philippe Waroquiers from comment #7) > If mmap would necessarily zero out memory, then > that would create major difficulties to use > shared memory. > I think that what the kernel guarantees is that > the first process that creates new memory > with mmap gets zero-ed memory Yes but I don't think valgrind knows if this shm page is mapped first time or N-th time. It simply doesn't have such info, unless I am missing something obvious. So it should probably assume the memory is initialized. Or does it check if the mapping is MAP_SHARED and assumes uninitialized only in that case? In either case, my latest test-case does mmap() then VALGRIND_MAKE_MEM_DEFINED() then fork(). No second mapping any more. > Initialising yourself the memory via one ptr > but accessing it via another mapping > is not the same as declaring the memory > defined after *each* mmap. > In the first case, valgrind can just detect that > the memory at ptr1 address is initialised, > but it cannot see this initialisation via > the second mapping. Well, my last test-case does only one mmap() and then fork(). So even if I think hard I don't see how can I satisfy your current suggestion. -- You are receiving this mail because: You are watching all bug changes.
