On 4/3/22 12:21, Peter Maydell wrote:
Currently qemu_try_memalign()'s behaviour if asked to allocate 0 bytes is rather variable: * on Windows, we will assert * on POSIX platforms, we get the underlying behaviour of the posix_memalign() or equivalent function, which may be either "return a valid non-NULL pointer" or "return NULL"Explictly check for 0 byte allocations, so we get consistent behaviour across platforms. We handle them by incrementing the size so that we return a valid non-NULL pointer that can later be passed to qemu_vfree(). This is permitted behaviour for the posix_memalign() API and is the most usual way that underlying malloc() etc implementations handle a zero-sized allocation request, because it won't trip up calling code that assumes NULL means an error. (This includes our own qemu_memalign(), which will abort on NULL.) This change is a preparation for sharing the qemu_try_memalign() code between Windows and POSIX. Signed-off-by: Peter Maydell <peter.mayd...@linaro.org> --- util/oslib-posix.c | 3 +++ util/oslib-win32.c | 4 +++- 2 files changed, 6 insertions(+), 1 deletion(-) diff --git a/util/oslib-posix.c b/util/oslib-posix.c index 0278902ee79..f7e22f4ff9b 100644 --- a/util/oslib-posix.c +++ b/util/oslib-posix.c @@ -209,6 +209,9 @@ void *qemu_try_memalign(size_t alignment, size_t size) g_assert(is_power_of_2(alignment)); }+ if (size == 0) {+ size++; + } #if defined(CONFIG_POSIX_MEMALIGN) int ret; ret = posix_memalign(&ptr, alignment, size); diff --git a/util/oslib-win32.c b/util/oslib-win32.c index 05857414695..8c28d70904d 100644 --- a/util/oslib-win32.c +++ b/util/oslib-win32.c @@ -48,12 +48,14 @@ void *qemu_try_memalign(size_t alignment, size_t size) { void *ptr;- g_assert(size != 0);
Better, X_try_Y() functions are not supposed to fail. Reviewed-by: Philippe Mathieu-Daudé <f4...@amsat.org>
