[clang] Reject incomplete type arguments for __builtin_dump_struct

[zyn0217]

We used to assume that the CXXRecordDecl passed to the 1st argument always had a definition. This is not true since a pointer to an incomplete type was not excluded.

Fixes #63506

[llvmbot]

@llvm/pr-subscribers-clang

Author: Younan Zhang (zyn0217)

Changes

We used to assume that the CXXRecordDecl passed to the 1st argument always had a definition. This is not true since a pointer to an incomplete type was not excluded.

---

Full diff: https://github.com/llvm/llvm-project/pull/72749.diff

4 Files Affected:

• (modified) clang/docs/LanguageExtensions.rst (+1-1)
• (modified) clang/docs/ReleaseNotes.rst (+3)
• (modified) clang/lib/Sema/SemaChecking.cpp (+5)
• (modified) clang/test/SemaCXX/builtin-dump-struct.cpp (+4)

diff --git a/clang/docs/LanguageExtensions.rst b/clang/docs/LanguageExtensions.rst
index 30e288f986782fd..e80a096357b1deb 100644
--- a/clang/docs/LanguageExtensions.rst
+++ b/clang/docs/LanguageExtensions.rst
@@ -2809,7 +2809,7 @@ Example output:
 
 The ``__builtin_dump_struct`` function is used to print the fields of a simple
 structure and their values for debugging purposes. The first argument of the
-builtin should be a pointer to the struct to dump. The second argument ``f``
+builtin should be a pointer to a complete record type to dump. The second argument ``f``
 should be some callable expression, and can be a function object or an overload
 set. The builtin calls ``f``, passing any further arguments ``args...``
 followed by a ``printf``-compatible format string and the corresponding
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 74358219ba9fb22..f2903c1684dcb60 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -691,6 +691,9 @@ Bug Fixes to C++ Support
   Fixes:
   (`#68769 <https://github.com/llvm/llvm-project/issues/68769>`_)
 
+- Clang now rejects incomplete types for ``__builtin_dump_struct``. Fixes:
+  (`#63506 <https://github.com/llvm/llvm-project/issues/63506>`_)
+
 - Clang now defers the instantiation of explicit specifier until constraint checking
   completes (except deduction guides). Fixes:
   (`#59827 <https://github.com/llvm/llvm-project/issues/59827>`_)
diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index ae588db02bbe722..20ff3ce722da80a 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -713,6 +713,11 @@ static ExprResult SemaBuiltinDumpStruct(Sema &S, CallExpr *TheCall) {
     return ExprError();
   }
   const RecordDecl *RD = PtrArgType->getPointeeType()->getAsRecordDecl();
+  if (!RD->isCompleteDefinition()) {
+    S.Diag(PtrArgResult.get()->getBeginLoc(), diag::err_incomplete_type)
+        << PtrArgType->getPointeeType();
+    return ExprError();
+  }
 
   // Second argument is a callable, but we can't fully validate it until we try
   // calling it.
diff --git a/clang/test/SemaCXX/builtin-dump-struct.cpp b/clang/test/SemaCXX/builtin-dump-struct.cpp
index b3d2a2d808ce267..477bbcf07a41fa4 100644
--- a/clang/test/SemaCXX/builtin-dump-struct.cpp
+++ b/clang/test/SemaCXX/builtin-dump-struct.cpp
@@ -149,7 +149,10 @@ B {
 }
 )"[1]);
 
+class Incomplete;
+
 void errors(B b) {
+  ConstexprString cs;
   __builtin_dump_struct(); // expected-error {{too few arguments to function call, expected 2, have 0}}
   __builtin_dump_struct(1); // expected-error {{too few arguments to function call, expected 2, have 1}}
   __builtin_dump_struct(1, 2); // expected-error {{expected pointer to struct as 1st argument to '__builtin_dump_struct', found 'int'}}
@@ -157,6 +160,7 @@ void errors(B b) {
   __builtin_dump_struct(&b, Format, 0); // expected-error {{no matching function for call to 'Format'}}
                                         // expected-note@-1 {{in call to printing function with arguments '(0, "%s", "B")' while dumping struct}}
                                         // expected-note@#Format {{no known conversion from 'int' to 'ConstexprString &' for 1st argument}}
+  __builtin_dump_struct((Incomplete *)nullptr, Format, cs); // expected-error {{incomplete type 'Incomplete' where a complete type is required}}
 }
 #endif
 

[shafik]

LGTM you should put the bug report in the problem description so it automatically links the PR and closes it when you merge it.

[zyn0217]

Thanks! Added the link.