[clang] [clang] Fix unexpected warnings after a01307a (PR #75591)

[Mariya Podchishchaeva via cfe-commits]

https://github.com/Fznamznon updated https://github.com/llvm/llvm-project/pull/75591

>From 7d93f51878c495e245ce21d4be97c4ca7cddd404 Mon Sep 17 00:00:00 2001
From: "Podchishchaeva, Mariya" <mariya.podchishchaeva at intel.com>
Date: Fri, 15 Dec 2023 04:05:41 -0800
Subject: [PATCH 1/2] [clang] Fix unexpected warnings after a01307a

a01307a broke silencing of -Wmissing-field-initializers warnings in C for
nested designators. This fixes the issue.
---
 clang/lib/Sema/SemaInit.cpp                  |  8 +++++++
 clang/test/Sema/missing-field-initializers.c | 23 ++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index de0d92edb550dd..1cd2198503abaf 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -864,6 +864,14 @@ InitListChecker::FillInEmptyInitializations(const InitializedEntity &Entity,
       WarnIfMissingField &=
           SemaRef.getLangOpts().CPlusPlus || !hasAnyDesignatedInits(SForm);
 
+      if (OuterILE) {
+        InitListExpr *OuterSForm = OuterILE->isSyntacticForm()
+                                       ? OuterILE
+                                       : OuterILE->getSyntacticForm();
+        WarnIfMissingField &= SemaRef.getLangOpts().CPlusPlus ||
+                              !hasAnyDesignatedInits(OuterSForm);
+      }
+
       unsigned NumElems = numStructUnionElements(ILE->getType());
       if (!RDecl->isUnion() && RDecl->hasFlexibleArrayMember())
         ++NumElems;
diff --git a/clang/test/Sema/missing-field-initializers.c b/clang/test/Sema/missing-field-initializers.c
index 8653591ff1187a..8dc8288ad92e6c 100644
--- a/clang/test/Sema/missing-field-initializers.c
+++ b/clang/test/Sema/missing-field-initializers.c
@@ -61,3 +61,26 @@ struct S {
 // f1, now we no longer issue that warning (note, this code is still unsafe
 // because of the buffer overrun).
 struct S s = {1, {1, 2}};
+
+struct S1 {
+  long int l;
+  struct  { int a, b; } d1;
+};
+
+struct S1 s01 = { 1, {1} }; // expected-warning {{missing field 'b' initializer}}
+struct S1 s02 = { .d1.a = 1 }; // designator avoids MFI warning
+
+union U1 {
+  long int l;
+  struct  { int a, b; } d1;
+};
+
+union U1 u01 = { 1 };
+union U1 u02 = { .d1.a = 1 }; // designator avoids MFI warning
+
+struct S2 {
+  long int l;
+  struct { int a, b; struct {int c; } d2; } d1;
+};
+
+struct S2 s22 = { .d1.d2.c = 1 }; // designator avoids MFI warning

>From d779611237a5a4b8824c011a09639ff4f745fd23 Mon Sep 17 00:00:00 2001
From: "Podchishchaeva, Mariya" <mariya.podchishchaeva at intel.com>
Date: Fri, 15 Dec 2023 05:29:56 -0800
Subject: [PATCH 2/2] Add comment

---
 clang/lib/Sema/SemaInit.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index 1cd2198503abaf..035eaae58965a4 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -865,6 +865,9 @@ InitListChecker::FillInEmptyInitializations(const InitializedEntity &Entity,
           SemaRef.getLangOpts().CPlusPlus || !hasAnyDesignatedInits(SForm);
 
       if (OuterILE) {
+        // When nested designators are present, there might be two nested init
+        // lists created and only outer will contain designated initializer
+        // expression, so check outer list as well.
         InitListExpr *OuterSForm = OuterILE->isSyntacticForm()
                                        ? OuterILE
                                        : OuterILE->getSyntacticForm();