On Tue, Jan 19, 2021 at 03:37:25PM -0500, Jason Merrill wrote:
> On 1/12/21 9:13 PM, Marek Polacek wrote:
> > Another ICE with delayed noexcept parsing, but a bit gnarlier.
> >
> > A function definition marked with __attribute__((used)) ought to be
> > emitted even when it is not referenced in a TU. For a member function
> > template marked with __attribute__((used)) this means that it will
> > be instantiated: in instantiate_class_template_1 we have
> >
> > 11971 /* Instantiate members marked with attribute used. */
> > 11972 if (r != error_mark_node && DECL_PRESERVE_P (r))
> > 11973 mark_used (r);
> >
> > It is not so surprising that this doesn't work well with delayed
> > noexcept parsing: when we're processing the function template we delay
> > the parsing, so the member "foo" is found, but then when we're
> > instantiating it, "foo" hasn't yet been seen, which creates a
> > discrepancy and a crash ensues. "foo" hasn't yet been seen because
> > instantiate_class_template_1 just loops over the class members and
> > instantiates right away.
>
> That seems like the bug; we shouldn't instantiate any members until we're
> done instantiating the class.
I reckon we can make it work, then:
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
-- >8 --
Another ICE with delayed noexcept parsing, but a bit gnarlier.
A function definition marked with __attribute__((used)) ought to be
emitted even when it is not referenced in the TU. For a member function
template marked with __attribute__((used)) this means that it will
be instantiated: in instantiate_class_template_1 we have
11971 /* Instantiate members marked with attribute used. */
11972 if (r != error_mark_node && DECL_PRESERVE_P (r))
11973 mark_used (r);
It is not so surprising that this doesn't work well with delayed
noexcept parsing: when we're processing the function template we delay
the parsing, so the member "foo" is found, but then when we're
instantiating it, "foo" hasn't yet been seen, which creates a
discrepancy and a crash ensues. "foo" hasn't yet been seen because
instantiate_class_template_1 just loops over the class members and
instantiates right away.
To make it work, this patch uses a vector to keep track of members
marked with attribute used and uses it to instantiate such members
only after we're done with the class; in particular, after we have
called finish_member_declaration for each member. And we ought to
be verifying that we did emit such members, so I've added a bunch
of dg-finals.
gcc/cp/ChangeLog:
PR c++/97966
* pt.c (instantiate_class_template_1): Instantiate members
marked with attribute used only after we're done instantiating
the class.
gcc/testsuite/ChangeLog:
PR c++/97966
* g++.dg/cpp0x/noexcept63.C: New test.
---
gcc/cp/pt.c | 12 ++++-
gcc/testsuite/g++.dg/cpp0x/noexcept63.C | 63 +++++++++++++++++++++++++
2 files changed, 73 insertions(+), 2 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/noexcept63.C
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 373f8279604..81c78322a46 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -11895,6 +11895,9 @@ instantiate_class_template_1 (tree type)
relative to the scope of the class. */
pop_to_parent_deferring_access_checks ();
+ /* A vector to hold members marked with attribute used. */
+ auto_vec<tree> used;
+
/* Now members are processed in the order of declaration. */
for (member = CLASSTYPE_DECL_LIST (pattern);
member; member = TREE_CHAIN (member))
@@ -11968,7 +11971,7 @@ instantiate_class_template_1 (tree type)
finish_member_declaration (r);
/* Instantiate members marked with attribute used. */
if (r != error_mark_node && DECL_PRESERVE_P (r))
- mark_used (r);
+ used.safe_push (r);
if (TREE_CODE (r) == FUNCTION_DECL
&& DECL_OMP_DECLARE_REDUCTION_P (r))
cp_check_omp_declare_reduction (r);
@@ -12034,7 +12037,7 @@ instantiate_class_template_1 (tree type)
/*flags=*/0);
/* Instantiate members marked with attribute used. */
if (r != error_mark_node && DECL_PRESERVE_P (r))
- mark_used (r);
+ used.safe_push (r);
}
else if (TREE_CODE (r) == FIELD_DECL)
{
@@ -12185,6 +12188,11 @@ instantiate_class_template_1 (tree type)
}
}
+ /* Now that we've gone through all the members, instantiate those
+ marked with attribute used. */
+ for (tree &x : used)
+ mark_used (x);
+
if (fn_context)
{
/* Restore these before substituting into the lambda capture
diff --git a/gcc/testsuite/g++.dg/cpp0x/noexcept63.C
b/gcc/testsuite/g++.dg/cpp0x/noexcept63.C
new file mode 100644
index 00000000000..cf048f56c2a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/noexcept63.C
@@ -0,0 +1,63 @@
+// PR c++/97966
+// { dg-do compile { target c++11 } }
+
+template <int>
+struct S1 {
+ __attribute__((used)) S1() noexcept(noexcept(this->foo())) { }
+ void foo();
+};
+
+template <int>
+struct S2 {
+ __attribute__((used)) void bar() noexcept(noexcept(this->foo())) { }
+ void foo();
+};
+
+template <int>
+struct S3 {
+ void __attribute__((used)) bar() noexcept(noexcept(this->foo())) { }
+ void foo();
+};
+
+template <int>
+struct S4 {
+ [[gnu::used]] void bar() noexcept(noexcept(this->foo())) { }
+ void foo();
+};
+
+template <int>
+struct S5 {
+ void bar() noexcept(noexcept(this->foo())) __attribute__((used)) { }
+ void foo();
+};
+
+template <int>
+struct S6 {
+ template <int>
+ struct N {
+ [[gnu::used]] void bar() noexcept(noexcept(this->foo())) { }
+ void foo();
+ };
+};
+
+void
+g ()
+{
+ S1<1> s1;
+ S2<1> s2;
+ S3<1> s3;
+ S4<1> s4;
+ S5<1> s5;
+ S6<1>::N<1> n;
+}
+
+// Make sure that we did emit the functions marked with attribute used
+// even though they're not referenced in this TU. (Well, the S1()
+// constructor is.)
+// { dg-final { scan-assembler "_ZN2S1ILi1EEC1Ev" } }
+// { dg-final { scan-assembler "_ZN2S1ILi1EEC2Ev" } }
+// { dg-final { scan-assembler "_ZN2S2ILi1EE3barEv" } }
+// { dg-final { scan-assembler "_ZN2S3ILi1EE3barEv" } }
+// { dg-final { scan-assembler "_ZN2S4ILi1EE3barEv" } }
+// { dg-final { scan-assembler "_ZN2S5ILi1EE3barEv" } }
+// { dg-final { scan-assembler "_ZN2S6ILi1EE1NILi1EE3barEv" } }
base-commit: b93d0e36c0a86c3d15310fe7383321ca63aeb04d
--
2.29.2
