The improved checking of flexible array members committed in r231665
(and later) deliberately excluded anonymous structs and unions
(unnamed members of types with no tags) to allow a harmless extension
that was accepted by G++ prior to the change. However, being overly
broad, the exemption prevents flexible array members that are invalid
for other reasons from being diagnosed in these contexts. That in
turn leads to a subset of such cases causing ICEs downstream.
The attached trivial patch tightens up the conditions under which
this extension is accepted: it only considers such structs when they
are members, thus eliminating the ICE.
Tested on x86_64-linux.
Martin
PR c++/93753 - ICE on a flexible array followed by a member in an anonymous struct with an initializer
gcc/cp/ChangeLog:
PR gcov-profile/93753
* class.c (check_flexarrays): Tighten up a test for potential members
of anonymous structs or unions.
gcc/testsuite/ChangeLog:
PR gcov-profile/93753
* g++.dg/ext/flexary36.C: New test.
* g++.dg/lto/pr93166_0.C: Make struct with flexarray valid.
diff --git a/gcc/cp/class.c b/gcc/cp/class.c
index a1fd1aa91cc..772134df5fc 100644
--- a/gcc/cp/class.c
+++ b/gcc/cp/class.c
@@ -7142,6 +7142,8 @@ check_flexarrays (tree t, flexmems_t *fmem /* = NULL */,
/* Is the type unnamed (and therefore a member of it potentially
an anonymous struct or union)? */
bool maybe_anon_p = TYPE_UNNAMED_P (t);
+ if (tree ctx = maybe_anon_p ? TYPE_CONTEXT (t) : NULL_TREE)
+ maybe_anon_p = RECORD_OR_UNION_TYPE_P (ctx);
/* Search the members of the current (possibly derived) class, skipping
unnamed structs and unions since those could be anonymous. */
diff --git a/gcc/testsuite/g++.dg/ext/flexary36.C b/gcc/testsuite/g++.dg/ext/flexary36.C
new file mode 100644
index 00000000000..220ccc0ccf8
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/flexary36.C
@@ -0,0 +1,123 @@
+/* PR c++/93753 - ICE on a flexible array followed by a member in
+ an anonymous struct with an initializer
+ { dg-do compile }
+ { dg-options "-Wall -Wno-unused-variable" } */
+
+struct {
+ int a[]; // { dg-error "flexible array member '<unnamed struct>::a' not at end of 'struct<unnamed>'" }
+ int b;
+} ax;
+
+struct {
+ int a[]; // { dg-error "flexible array member '<unnamed struct>::a' not at end of 'struct<unnamed>'" }
+ int b;
+} bx = { };
+
+struct {
+ int a[]; // { dg-error "flexible array member '<unnamed struct>::a' not at end of 'struct<unnamed>'" }
+ int b;
+} cx = { 0 };
+
+struct {
+ int a[]; // { dg-error "flexible array member '<unnamed struct>::a' not at end of 'struct<unnamed>'" }
+ int b;
+} dx = { 1 };
+
+
+union {
+ int a[]; // { dg-error "flexible array member in union" }
+ int b;
+} du = { 1 };
+
+
+struct A {
+ int a[]; // { dg-error "flexible array member 'A::a' not at end of 'struct A'" }
+ int b;
+} a;
+
+struct B {
+ int a[]; // { dg-error "flexible array member 'B::a' not at end of 'struct B'" }
+ int b;
+} b = { };
+
+struct C {
+ int a[]; // { dg-error "flexible array member 'C::a' not at end of 'struct C'" }
+ int b;
+} c = { 0 };
+
+struct D {
+ int a[]; // { dg-error "flexible array member 'D::a' not at end of 'struct D'" }
+ int b;
+} d = { 1 };
+
+
+struct E {
+ struct {
+ int a[]; // { dg-error " not at end " }
+ int b;
+ } e = { 1 }; // { dg-error "non-static initialization of a flexible array member" }
+};
+
+struct G {
+ struct {
+ int a[]; // { dg-error " not at end " }
+ int b;
+ };
+} g = { 1 }; // { dg-error "initialization of flexible array member in a nested context" }
+
+struct H {
+ int i;
+ struct {
+ int a[]; // { dg-error " not at end " }
+ int b;
+ };
+} h = { 1 };
+
+namespace {
+
+struct {
+ int a[]; // { dg-error " not at end of " }
+ int b;
+} ax;
+
+struct {
+ int a[]; // { dg-error " not at end " }
+ int b;
+} bx = { };
+
+struct {
+ int a[]; // { dg-error " not at end " }
+ int b;
+} cx = { 0 };
+
+struct {
+ int a[]; // { dg-error " not at end " }
+ int b;
+} dx = { 1 };
+
+
+struct A {
+ int a[]; // { dg-error " not at end of 'struct {anonymous}::A'" }
+ int b;
+} a;
+
+struct B {
+ int a[]; // { dg-error " not at end of 'struct {anonymous}::B'" }
+ int b;
+} b = { };
+
+struct C {
+ int a[]; // { dg-error " not at end of 'struct {anonymous}::C'" }
+ int b;
+} c = { 0 };
+
+struct D {
+ int a[]; // { dg-error " not at end of 'struct {anonymous}::D'" }
+ int b;
+} d = { 1 };
+
+}
+
+// { dg-prune-output "unnamed type with no linkage used to declare variable" }
+// { dg-prune-output "non-static data member initializers" }
+// { dg-prune-output "extended initializer lists" }
diff --git a/gcc/testsuite/g++.dg/lto/pr93166_0.C b/gcc/testsuite/g++.dg/lto/pr93166_0.C
index 52f7ddf4016..a83ba6e0400 100644
--- a/gcc/testsuite/g++.dg/lto/pr93166_0.C
+++ b/gcc/testsuite/g++.dg/lto/pr93166_0.C
@@ -109,7 +109,7 @@ public:
QSignalMapper *m_sortSignalMapper;
};
struct {
- int data[];
+ int n, data[];
} b;
unsigned c[]{};
void TreeView::qt_static_metacall(QObject *p1, QMetaObject::Call, int,
