As per the C spec, it is illegal to alias pointers to different types. This results in undefined behaviour after optimization passes, resulting in very subtle bugs that happen only on a full moon..
Use a memcpy() as a well defined coercion between the double to uint64_t interpretations of the memory. V.2: Use static_assert() instead of assert(). V.3: Use C99 compat STATIC_ASSERT() over C11 static_assert(). Signed-off-by: Edward O'Callaghan <[email protected]> --- src/gallium/drivers/virgl/virgl_encode.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/src/gallium/drivers/virgl/virgl_encode.c b/src/gallium/drivers/virgl/virgl_encode.c index be72f70..85843b7 100644 --- a/src/gallium/drivers/virgl/virgl_encode.c +++ b/src/gallium/drivers/virgl/virgl_encode.c @@ -21,6 +21,8 @@ * USE OR OTHER DEALINGS IN THE SOFTWARE. */ #include <stdint.h> +#include <assert.h> +#include <string.h> #include "util/u_format.h" #include "util/u_memory.h" @@ -315,12 +317,16 @@ int virgl_encode_clear(struct virgl_context *ctx, double depth, unsigned stencil) { int i; + uint64_t qword; + + STATIC_ASSERT(sizeof(qword) == sizeof(depth)); + memcpy(&qword, &depth, sizeof(qword)); virgl_encoder_write_cmd_dword(ctx, VIRGL_CMD0(VIRGL_CCMD_CLEAR, 0, VIRGL_OBJ_CLEAR_SIZE)); virgl_encoder_write_dword(ctx->cbuf, buffers); for (i = 0; i < 4; i++) virgl_encoder_write_dword(ctx->cbuf, color->ui[i]); - virgl_encoder_write_qword(ctx->cbuf, *(uint64_t *)&depth); + virgl_encoder_write_qword(ctx->cbuf, qword); virgl_encoder_write_dword(ctx->cbuf, stencil); return 0; } -- 2.9.3 _______________________________________________ mesa-dev mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/mesa-dev
