Hi!
As mentioned in the PR, various x86 intrinsics need to return
an uninitialized vector. Currently they use self initialization
to avoid -Wuninitialized warnings, which works fine in C, but
doesn't work in C++ where -Winit-self is enabled in -Wall.
We don't have an attribute to mark a variable as knowingly
uninitialized (the uninitialized attribute exists but means
something else, only in the -ftrivial-auto-var-init context),
and trying to suppress either -Wuninitialized or -Winit-self
inside of the _mm_undefined_ps etc. intrinsic definitions
doesn't work, one needs to currently disable through pragmas
-Wuninitialized warning at the point where _mm_undefined_ps etc.
result is actually used, but that goes against the intent of
those intrinsics.
The -Winit-self warning option actually doesn't do any warning,
all we do is record a suppression for -Winit-self if !warn_init_self
on the decl definition and later look that up in uninit pass.
The following patch changes those !warn_init_self tests which
are true only based on the command line option setting, not based
on GCC diagnostic pragma overrides to
!warning_enabled_at (DECL_SOURCE_LOCATION (decl), OPT_Winit_self)
such that it takes them into account.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
Will post incremental patch for the intrinsic headers.
2023-01-13 Jakub Jelinek <ja...@redhat.com>
PR c++/105593
gcc/c/
* c-parser.cc (c_parser_initializer): Check warning_enabled_at
at the DECL_SOURCE_LOCATION (decl) for OPT_Winit_self instead
of warn_init_self.
gcc/cp/
* decl.cc (cp_finish_decl): Check warning_enabled_at
at the DECL_SOURCE_LOCATION (decl) for OPT_Winit_self instead
of warn_init_self.
gcc/testsuite/
* c-c++-common/Winit-self3.c: New test.
* c-c++-common/Winit-self4.c: New test.
* c-c++-common/Winit-self5.c: New test.
--- gcc/c/c-parser.cc.jj 2023-01-11 22:18:25.560492345 +0100
+++ gcc/c/c-parser.cc 2023-01-12 15:30:10.460233783 +0100
@@ -5701,7 +5701,7 @@ c_parser_initializer (c_parser *parser,
&& !DECL_EXTERNAL (decl)
&& !TREE_STATIC (decl)
&& ret.value == decl
- && !warn_init_self)
+ && !warning_enabled_at (DECL_SOURCE_LOCATION (decl), OPT_Winit_self))
suppress_warning (decl, OPT_Winit_self);
if (TREE_CODE (ret.value) != STRING_CST
&& (TREE_CODE (ret.value) != COMPOUND_LITERAL_EXPR
--- gcc/cp/decl.cc.jj 2023-01-04 18:42:24.597997547 +0100
+++ gcc/cp/decl.cc 2023-01-12 15:26:01.257817526 +0100
@@ -8407,7 +8407,7 @@ cp_finish_decl (tree decl, tree init, bo
if (!DECL_EXTERNAL (decl)
&& !TREE_STATIC (decl)
&& decl == tree_strip_any_location_wrapper (init)
- && !warn_init_self)
+ && !warning_enabled_at (DECL_SOURCE_LOCATION (decl), OPT_Winit_self))
suppress_warning (decl, OPT_Winit_self);
}
--- gcc/testsuite/c-c++-common/Winit-self3.c.jj 2023-01-12 15:49:56.759172518
+0100
+++ gcc/testsuite/c-c++-common/Winit-self3.c 2023-01-12 15:50:51.512384963
+0100
@@ -0,0 +1,36 @@
+/* PR c++/105593 */
+/* { dg-do compile } */
+/* { dg-options "-W -Wall" } */
+
+void bar (int);
+
+static inline int
+baz (void)
+{
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Winit-self"
+ int u = u; /* { dg-bogus "'u' is used uninitialized" } */
+#pragma GCC diagnostic pop
+ return u;
+}
+
+void
+foo (void)
+{
+ int u = baz ();
+ bar (u);
+}
+
+static inline int
+qux (void)
+{
+ int u = u; /* { dg-warning "'u' is used uninitialized" "" { target
c++ } } */
+ return u; /* { dg-message "'u' was declared here" "" { target c++
} .-1 } */
+}
+
+void
+corge (void)
+{
+ int u = qux ();
+ bar (u);
+}
--- gcc/testsuite/c-c++-common/Winit-self4.c.jj 2023-01-12 15:50:15.233906776
+0100
+++ gcc/testsuite/c-c++-common/Winit-self4.c 2023-01-12 15:50:42.445515372
+0100
@@ -0,0 +1,36 @@
+/* PR c++/105593 */
+/* { dg-do compile } */
+/* { dg-options "-W -Wall -Winit-self" } */
+
+void bar (int);
+
+static inline int
+baz (void)
+{
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Winit-self"
+ int u = u; /* { dg-bogus "'u' is used uninitialized" } */
+#pragma GCC diagnostic pop
+ return u;
+}
+
+void
+foo (void)
+{
+ int u = baz ();
+ bar (u);
+}
+
+static inline int
+qux (void)
+{
+ int u = u; /* { dg-warning "'u' is used uninitialized" } */
+ return u; /* { dg-message "'u' was declared here" "" { target
*-*-* } .-1 } */
+}
+
+void
+corge (void)
+{
+ int u = qux ();
+ bar (u);
+}
--- gcc/testsuite/c-c++-common/Winit-self5.c.jj 2023-01-12 15:51:01.045247847
+0100
+++ gcc/testsuite/c-c++-common/Winit-self5.c 2023-01-12 15:51:12.929076923
+0100
@@ -0,0 +1,36 @@
+/* PR c++/105593 */
+/* { dg-do compile } */
+/* { dg-options "-W -Wall -Wno-init-self" } */
+
+void bar (int);
+
+static inline int
+baz (void)
+{
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Winit-self"
+ int u = u; /* { dg-bogus "'u' is used uninitialized" } */
+#pragma GCC diagnostic pop
+ return u;
+}
+
+void
+foo (void)
+{
+ int u = baz ();
+ bar (u);
+}
+
+static inline int
+qux (void)
+{
+ int u = u; /* { dg-bogus "'u' is used uninitialized" } */
+ return u;
+}
+
+void
+corge (void)
+{
+ int u = qux ();
+ bar (u);
+}
Jakub
