[clang] [Clang] disallow constexpr with auto and explicit type in C23 (PR #163469)
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cfe-commits at lists.llvm.org
Fri Oct 17 17:47:08 PDT 2025
================
@@ -130,3 +130,30 @@ void atomic(void) {
void attributes(void) {
auto ident [[clang::annotate("this works")]] = 12; // c17-error {{type specifier missing, defaults to 'int'; ISO C99 and later do not support implicit int}}
}
+
+/** GH163090 */
+constexpr auto int a1 = 0; // c23-error {{illegal storage class on file-scoped variable}} \
+ c23-error {{cannot combine with previous 'auto' declaration specifier}} \
+ c17-error {{illegal storage class on file-scoped variable}} \
+ c17-error {{unknown type name 'constexpr'}}
+
+constexpr int auto a2 = 0; // c23-error {{cannot combine with previous 'int' declaration specifier}} \
+ c17-error {{illegal storage class on file-scoped variable}} \
+ c17-error {{unknown type name 'constexpr'}}
+
+auto int b1 = 0; // c23-error {{illegal storage class on file-scoped variable}} \
+ c17-error {{illegal storage class on file-scoped variable}}
+
+int auto b2 = 0; // c23-error {{cannot combine with previous 'int' declaration specifier}} \
+ c17-error {{illegal storage class on file-scoped variable}}
+
+void f() {
+ constexpr auto int c1 = 0; // c23-error {{cannot combine with previous 'auto' declaration specifier}} \
+ c17-error {{use of undeclared identifier 'constexpr'}}
+
+ constexpr int auto c2 = 0; // c23-error {{cannot combine with previous 'int' declaration specifier}} \
+ c17-error {{use of undeclared identifier 'constexpr'}}
+
+ auto int d1 = 0;
+ int auto d2 = 0; // c23-error {{cannot combine with previous 'int' declaration specifier}}
----------------
Halalaluyafail3 wrote:
Why is the order of keywords here significant?
https://github.com/llvm/llvm-project/pull/163469
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