Just tell the compiler that drm_event will alias the char buffer,
so that it has no excuse to warn or generate bad code.
Signed-off-by: Grazvydas Ignotas <notasas at gmail.com>
---
Android.mk | 1 +
configure.ac | 9 +++++++++
libdrm_macros.h | 6 ++++++
xf86drmMode.c | 11 +++++++----
4 files changed, 23 insertions(+), 4 deletions(-)
diff --git a/Android.mk b/Android.mk
index 2aa2bc9..ae7c3fe 100644
--- a/Android.mk
+++ b/Android.mk
@@ -42,6 +42,7 @@ LOCAL_C_INCLUDES := \
LOCAL_CFLAGS := \
-DHAVE_VISIBILITY=1 \
+ -DHAVE_MAY_ALIAS=1 \
-DHAVE_LIBDRM_ATOMIC_PRIMITIVES=1
include $(BUILD_STATIC_LIBRARY)
diff --git a/configure.ac b/configure.ac
index e0597c3..2868036 100644
--- a/configure.ac
+++ b/configure.ac
@@ -507,6 +507,15 @@ if test "x$HAVE_ATTRIBUTE_VISIBILITY" = xyes; then
AC_DEFINE(HAVE_VISIBILITY, 1, [Compiler supports
__attribute__(("hidden"))])
fi
+AC_MSG_CHECKING([whether $CC supports __attribute__((__may_alias__))])
+AC_LINK_IFELSE([AC_LANG_PROGRAM([
+ struct foo_may_alias { int i; } __attribute__((__may_alias__)) foo;
+])], HAVE_ATTRIBUTE_MAY_ALIAS="yes"; AC_MSG_RESULT([yes]),
AC_MSG_RESULT([no]));
+
+if test "x$HAVE_ATTRIBUTE_MAY_ALIAS" = xyes; then
+ AC_DEFINE(HAVE_MAY_ALIAS, 1, [Compiler supports
__attribute__((__may_alias__))])
+fi
+
AC_SUBST(WARN_CFLAGS)
AC_CONFIG_FILES([
Makefile
diff --git a/libdrm_macros.h b/libdrm_macros.h
index 639d090..eea47ee 100644
--- a/libdrm_macros.h
+++ b/libdrm_macros.h
@@ -29,6 +29,12 @@
# define drm_private
#endif
+#if defined(HAVE_MAY_ALIAS)
+# define drm_may_alias __attribute__((__may_alias__))
+#else
+# define drm_may_alias
+#endif
+
/**
* Static (compile-time) assertion.
diff --git a/xf86drmMode.c b/xf86drmMode.c
index fb22f68..a6bf5f7 100644
--- a/xf86drmMode.c
+++ b/xf86drmMode.c
@@ -52,6 +52,7 @@
#include <stdio.h>
#include <stdbool.h>
+#include "libdrm_macros.h"
#include "xf86drmMode.h"
#include "xf86drm.h"
#include <drm.h>
@@ -885,9 +886,11 @@ int drmModeCrtcSetGamma(int fd, uint32_t crtc_id, uint32_t
size,
int drmHandleEvent(int fd, drmEventContextPtr evctx)
{
+ struct drm_event_aliased {
+ struct drm_event e;
+ } drm_may_alias *e;
char buffer[1024];
int len, i;
- struct drm_event *e;
struct drm_event_vblank *vblank;
/* The DRM read semantics guarantees that we always get only
@@ -901,8 +904,8 @@ int drmHandleEvent(int fd, drmEventContextPtr evctx)
i = 0;
while (i < len) {
- e = (struct drm_event *) &buffer[i];
- switch (e->type) {
+ e = (struct drm_event_aliased *) &buffer[i];
+ switch (e->e.type) {
case DRM_EVENT_VBLANK:
if (evctx->version < 1 ||
evctx->vblank_handler == NULL)
@@ -928,7 +931,7 @@ int drmHandleEvent(int fd, drmEventContextPtr evctx)
default:
break;
}
- i += e->length;
+ i += e->e.length;
}
return 0;
--
2.7.4
