On 2/20/25 9:51 AM, Marek Polacek wrote:
Now with the test fixed.
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
-- >8 --
In this PR we crash in cxx_eval_constant_expression/GOTO_EXPR on:
gcc_assert (cxx_dialect >= cxx23);
The code obviously doesn't expect to see a goto pre-C++23. But we can
get here with the new prvalue optimization. In this test we found
ourselves in synthesize_method for X::X(). This function calls:
a) finish_function, which does cp_genericize -> ... -> genericize_c_loops,
which creates the GOTO_EXPR;
b) expand_or_defer_fn -> maybe_clone_body -> ... -> cp_fold_function
where we reach the new maybe_constant_init call and crash on the
goto.
Hmm, this looks like bad recursion; finish_function wants to fold before
genericize, but then beacuse maybe_clone_body calls finish_function, we
end up folding again after genericize.
Maybe we should call maybe_clone_body directly from finish_function
rather than from expand_or_defer?
But the patch is OK as is.
Since we can validly get to that assert, I think we should just remove
it. I don't see other similar asserts like this one.
PR c++/118928
gcc/cp/ChangeLog:
* constexpr.cc (cxx_eval_constant_expression) <case GOTO_EXPR>: Remove
an assert.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/constexpr-prvalue5.C: New test.
---
gcc/cp/constexpr.cc | 1 -
.../g++.dg/cpp0x/constexpr-prvalue5.C | 24 +++++++++++++++++++
2 files changed, 24 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-prvalue5.C
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index 59dd0668af3..c68666cc5dd 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -8691,7 +8691,6 @@ cxx_eval_constant_expression (const constexpr_ctx *ctx,
tree t,
*jump_target = TREE_OPERAND (t, 0);
else
{
- gcc_assert (cxx_dialect >= cxx23);
if (!ctx->quiet)
error_at (loc, "%<goto%> is not a constant expression");
*non_constant_p = true;
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-prvalue5.C
b/gcc/testsuite/g++.dg/cpp0x/constexpr-prvalue5.C
new file mode 100644
index 00000000000..1f847bbe183
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-prvalue5.C
@@ -0,0 +1,24 @@
+// PR c++/118928
+// { dg-do compile { target c++11 } }
+// { dg-options "-O" }
+
+using size_t = decltype(sizeof(0));
+
+namespace std {
+template <typename T> struct initializer_list {
+ const T *_M_array;
+ size_t _M_len;
+};
+struct S {
+ constexpr S(const char *); // { dg-warning "used but never defined" }
+};
+struct vector {
+ constexpr vector(initializer_list<S>) {}
+};
+}
+struct Y {
+ std::vector v;
+};
+struct X {
+ Y y{{""}};
+} x;
base-commit: a2755339c6c9832467c573d956e91565943ecdc1
