llvmorg-github-actions[bot] wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang
Author: Akash Manna (akash-manna-sky)
<details>
<summary>Changes</summary>
Fixes #<!-- -->218144
Fixes #<!-- -->193687
`ParseDirectDeclarator` stops right after a structured binding like `[a, b]`,
since nothing can follow it — but that check only covers the unparenthesized
form. For `([a, b])`, the binding gets parsed inside `ParseParenDeclarator`,
and the outer `ParseDirectDeclarator` doesn't notice — it carries on into its
suffix loop and parses a trailing `()` as a function declarator. `([a, b])()
{}` then looks like a function definition, so `ActOnStartOfFunctionDef` gets
handed a `DecompositionDecl` where it expects a `FunctionDecl`:
`cast<FunctionDecl>` asserts, or segfaults later without assertions —
that's #<!-- -->193687. (The `b;` in the report is noise; `([a])() {}` alone
crashes.)
This patch makes `ParseDirectDeclarator` stop as well when the parenthesized
declarator turns out to be a structured binding, so nothing can follow a
binding list, parenthesized or not. The declaration then takes the normal
variable path and hits the diagnostics we already have — `structured binding
declaration cannot be declared with parentheses`, then `expected expression`
for the empty `()` — same as `[a, b]() {}` today. No Sema changes; the parser
just stops building a declarator that can't exist.
LLM tools were used for this contribution. I've reviewed, built, and tested the
change myself before pushing.
---
Full diff: https://github.com/llvm/llvm-project/pull/219270.diff
3 Files Affected:
- (modified) clang/docs/ReleaseNotes.md (+4)
- (modified) clang/lib/Parse/ParseDecl.cpp (+5)
- (added) clang/test/Parser/GH218144.cpp (+30)
``````````diff
diff --git a/clang/docs/ReleaseNotes.md b/clang/docs/ReleaseNotes.md
index 332e0bfdb3a8b..aaad27bd47408 100644
--- a/clang/docs/ReleaseNotes.md
+++ b/clang/docs/ReleaseNotes.md
@@ -536,6 +536,10 @@ features cannot lower the translation-unit ABI level;
parameter that follows a parameter pack (e.g.
`template <typename... T> S::S(T..., int = 10) {}`). (#GH216211)
+- Fixed an assertion failure when a parenthesized structured binding declarator
+ was followed by a function declarator and body (e.g. ``([a, b])() {}``).
+ (#GH218144, #GH193687)
+
#### Bug Fixes to AST Handling
- Fixed a non-deterministic ordering of unused local typedefs that made
diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index 2bbc76fc7c4df..11ba2b81baacc 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -6862,6 +6862,11 @@ void Parser::ParseDirectDeclarator(Declarator &D) {
// Example: 'char (*X)' or 'int (*XX)(void)'
ParseParenDeclarator(D);
+ // As above, a structured binding declarator cannot be followed by any
+ // declarator chunks.
+ if (D.isDecompositionDeclarator())
+ return;
+
// If the declarator was parenthesized, we entered the declarator
// scope when parsing the parenthesized declarator, then exited
// the scope already. Re-enter the scope, if we need to.
diff --git a/clang/test/Parser/GH218144.cpp b/clang/test/Parser/GH218144.cpp
new file mode 100644
index 0000000000000..d915047ad52ea
--- /dev/null
+++ b/clang/test/Parser/GH218144.cpp
@@ -0,0 +1,30 @@
+// RUN: %clang_cc1 -std=c++17 -fsyntax-only -verify %s
+// RUN: %clang_cc1 -std=c++26 -fsyntax-only -verify %s
+
+b;([c,ac])(){}
+// expected-error@-1 2 {{a type specifier is required for all declarations}}
+// expected-error@-2 {{structured binding declaration cannot be declared with
parentheses}}
+// expected-error@-3 {{expected expression}}
+// expected-error@-4 {{expected ';' after top level declarator}}
+
+([d])(){d}
+// expected-error@-1 {{a type specifier is required for all declarations}}
+// expected-error@-2 {{structured binding declaration cannot be declared with
parentheses}}
+// expected-error@-3 {{expected expression}}
+// expected-error@-4 {{expected ';' after top level declarator}}
+
+auto ([a])() {}
+// expected-error@-1 {{structured binding declaration cannot be declared with
parentheses}}
+// expected-error@-2 {{expected expression}}
+// expected-error@-3 {{expected ';' after top level declarator}}
+
+auto (([x, y, z]))() {}
+// expected-error@-1 {{structured binding declaration cannot be declared with
parentheses}}
+// expected-error@-2 {{expected expression}}
+// expected-error@-3 {{expected ';' after top level declarator}}
+
+struct S {
+ ([m, n])() {}
+ // expected-error@-1 {{structured binding declaration not permitted in this
context}}
+ // expected-error@-2 {{expected ';' at end of declaration list}}
+};
``````````
</details>
https://github.com/llvm/llvm-project/pull/219270
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