[clang] Fix wrong warning about missing init for flexible array members

[Fznamznon]

9108897 shouldn't have removed an additional check that field has incomplete array type.

Fixes #66300

[llvmbot]

@llvm/pr-subscribers-clang

Changes

9108897 shouldn't have removed an additional check that field has incomplete array type.

Fixes #66300

Full diff: https://github.com/llvm/llvm-project/pull/66341.diff

2 Files Affected:

• (modified) clang/lib/Sema/SemaInit.cpp (+2-1)
• (modified) clang/test/Sema/missing-field-initializers.c (+8)

diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index 93f05e2e47285e4..cb57a2d1a555caa 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -2395,7 +2395,8 @@ void InitListChecker::CheckStructUnionTypes(
       if (HasDesignatedInit && InitializedFields.count(*it))
         continue;
 
-      if (!it->isUnnamedBitfield() && !it->hasInClassInitializer()) {
+      if (!it->isUnnamedBitfield() && !it->hasInClassInitializer() &&
+          !it->getType()->isIncompleteArrayType()) {
         SemaRef.Diag(IList->getSourceRange().getEnd(),
                      diag::warn_missing_field_initializers)
             << *it;
diff --git a/clang/test/Sema/missing-field-initializers.c b/clang/test/Sema/missing-field-initializers.c
index 90e0e2a345b08c6..39b2b55300184cc 100644
--- a/clang/test/Sema/missing-field-initializers.c
+++ b/clang/test/Sema/missing-field-initializers.c
@@ -50,3 +50,11 @@ struct { int:5; int a; int:5; int b; int:5; } noNamedImplicit[] = {
   { 1, 2 },
   { 1 } // expected-warning {{missing field 'b' initializer}}
 };
+
+// GH66300
+struct S {
+  int f0;
+  int f1[];
+};
+
+struct S s = {1, {1, 2}}; // No warning

[cor3ntin]

LGTM !
(double checking: this does not need a release note because it fixes something that was changed post 17 branch. Correct?)

[Fznamznon]

(double checking: this does not need a release note because it fixes something that was changed post 17 branch. Correct?)

Exactly. There is a release note for guilty change.

[shafik]

Thank you for the quick fix

[AaronBallman]

LGTM!