From 4c85ac0d7bb9749f1ac77c6969561724a4433594 Mon Sep 17 00:00:00 2001
From: chrchr-github <78114321+chrchr-github@users.noreply.github.com>
Date: Sat, 12 Mar 2022 06:16:29 +0100
Subject: [PATCH] Fix #10852 FP unused struct member (inner struct in C code)
 (#3890)

* Fix #10852 FP unused struct member (inner struct in C code)

* Redundant findType() call, add test
---
 lib/symboldatabase.cpp | 24 +++++++++++++++++++++++-
 lib/symboldatabase.h   |  2 +-
 test/testunusedvar.cpp | 33 ++++++++++++++++++++++++++++++++-
 3 files changed, 56 insertions(+), 3 deletions(-)

diff --git a/lib/symboldatabase.cpp b/lib/symboldatabase.cpp
index 479069e64..97d849f10 100644
--- a/lib/symboldatabase.cpp
+++ b/lib/symboldatabase.cpp
@@ -5423,11 +5423,16 @@ const Scope *SymbolDatabase::findScopeByName(const std::string& name) const
 
 //---------------------------------------------------------------------------
 
-const Scope *Scope::findRecordInNestedList(const std::string & name) const
+const Scope *Scope::findRecordInNestedList(const std::string & name, bool isC) const
 {
     for (const Scope* scope: nestedList) {
         if (scope->className == name && scope->type != eFunction)
             return scope;
+        if (isC) {
+            const Scope* nestedScope = scope->findRecordInNestedList(name, isC);
+            if (nestedScope)
+                return nestedScope;
+        }
     }
 
     const Type * nested_type = findType(name);
@@ -5546,6 +5551,23 @@ const Type* SymbolDatabase::findType(const Token *startTok, const Scope *startSc
     if (startTok->str() == startScope->className && startScope->isClassOrStruct() && startTok->strAt(1) != "::")
         return startScope->definedType;
 
+    if (mTokenizer->isC()) {
+        const Scope* scope = startScope;
+        while (scope) {
+            if (startTok->str() == scope->className && scope->isClassOrStruct())
+                return scope->definedType;
+            const Scope* typeScope = scope->findRecordInNestedList(startTok->str(), /*isC*/ true);
+            if (typeScope) {
+                if (startTok->str() == typeScope->className && typeScope->isClassOrStruct()) {
+                    if (const Type* type = typeScope->definedType)
+                        return type;
+                }
+            }
+            scope = scope->nestedIn;
+        }
+        return nullptr;
+    }
+
     const Scope* start_scope = startScope;
 
     // absolute path - directly start in global scope
diff --git a/lib/symboldatabase.h b/lib/symboldatabase.h
index 3d0a4be89..34d639fcd 100644
--- a/lib/symboldatabase.h
+++ b/lib/symboldatabase.h
@@ -1129,7 +1129,7 @@ public:
      */
     const Function *findFunction(const Token *tok, bool requireConst=false) const;
 
-    const Scope *findRecordInNestedList(const std::string & name) const;
+    const Scope *findRecordInNestedList(const std::string & name, bool isC = false) const;
     Scope *findRecordInNestedList(const std::string & name) {
         return const_cast<Scope *>(const_cast<const Scope *>(this)->findRecordInNestedList(name));
     }
diff --git a/test/testunusedvar.cpp b/test/testunusedvar.cpp
index 4ee0711b1..d937b9d88 100644
--- a/test/testunusedvar.cpp
+++ b/test/testunusedvar.cpp
@@ -66,7 +66,7 @@ private:
         TEST_CASE(structmember16); // #10485
         TEST_CASE(structmember17); // #10591
         TEST_CASE(structmember18); // #10684
-        TEST_CASE(structmember19); // #10826, #10848
+        TEST_CASE(structmember19); // #10826, #10848, #10852
 
         TEST_CASE(localvar1);
         TEST_CASE(localvar2);
@@ -1710,6 +1710,37 @@ private:
                                "}\n");
         ASSERT_EQUALS("[test.cpp:1]: (style) struct member 'A::i' is never used.\n",
                       errout.str());
+
+        settings.enforcedLang = Settings::C;
+        checkStructMemberUsage("struct A {\n" // #10852
+                               "    struct B {\n"
+                               "        int x;\n"
+                               "    } b;\n"
+                               "} a;\n"
+                               "void f() {\n"
+                               "    struct B* pb = &a.b;\n"
+                               "    pb->x = 1;\n"
+                               "}\n");
+        ASSERT_EQUALS("", errout.str());
+
+        checkStructMemberUsage("union U {\n"
+                               "    struct A {\n"
+                               "        struct B {\n"
+                               "            int x;\n"
+                               "        } b;\n"
+                               "    } a;\n"
+                               "    struct C {\n"
+                               "        short s[2];\n"
+                               "    } c;\n"
+                               "} u;\n"
+                               "void f() {\n"
+                               "    struct B* pb = &u.a.b;\n"
+                               "    pb->x = 1;\n"
+                               "    struct C* pc = &u.c;\n"
+                               "    pc->s[0] = 1;\n"
+                               "}\n");
+        ASSERT_EQUALS("", errout.str());
+        settings.enforcedLang = Settings::None;
     }
 
     void functionVariableUsage_(const char* file, int line, const char code[], const char filename[] = "test.cpp") {