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[clang] Fix C23 constexpr crashes (#112708)

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Before using a constexpr variable that is not properly initialized check
that it is valid.

Fixes https://github.com/llvm/llvm-project/issues/109095
Fixes https://github.com/llvm/llvm-project/issues/112516
This commit is contained in:
Mariya Podchishchaeva 2024-10-18 10:18:34 +02:00 committed by Tobias Hieta
parent 81005af65f
commit c9e8540d6c
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GPG Key ID: 44F2485E45D59042
2 changed files with 24 additions and 3 deletions
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10
clang/lib/AST/Decl.cpp
View File

@ -2503,7 +2503,8 @@ bool VarDecl::isUsableInConstantExpressions(const ASTContext &Context) const {
if (!DefVD->mightBeUsableInConstantExpressions(Context))
return false;
// ... and its initializer is a constant initializer.
if (Context.getLangOpts().CPlusPlus && !DefVD->hasConstantInitialization())
if ((Context.getLangOpts().CPlusPlus || getLangOpts().C23) &&
!DefVD->hasConstantInitialization())
return false;
// C++98 [expr.const]p1:
// An integral constant-expression can involve only [...] const variables
@ -2610,8 +2611,11 @@ bool VarDecl::hasICEInitializer(const ASTContext &Context) const {
}
bool VarDecl::hasConstantInitialization() const {
// In C, all globals (and only globals) have constant initialization.
if (hasGlobalStorage() && !getASTContext().getLangOpts().CPlusPlus)
// In C, all globals and constexpr variables should have constant
// initialization. For constexpr variables in C check that initializer is a
// constant initializer because they can be used in constant expressions.
if (hasGlobalStorage() && !getASTContext().getLangOpts().CPlusPlus &&
!isConstexpr())
return true;
// In C++, it depends on whether the evaluation at the point of definition

17
clang/test/Sema/constexpr.c
View File

@ -364,3 +364,20 @@ void constexprif() {
void constevalif() {
if consteval (300) {} //expected-error {{expected '(' after 'if'}}
}
struct S11 {
int len;
};
void ghissue112516() {
struct S11 *s11 = 0;
constexpr int num = s11->len; // expected-error {{constexpr variable 'num' must be initialized by a constant expression}}
void *Arr[num];
}
void ghissue109095() {
constexpr char c[] = { 'a' };
constexpr int i = c[1]; // expected-error {{constexpr variable 'i' must be initialized by a constant expression}}\
// expected-note {{declared here}}
_Static_assert(i == c[0]); // expected-error {{static assertion expression is not an integral constant expression}}\
// expected-note {{initializer of 'i' is not a constant expression}}
}