From 557263acde16f23e73dfab1505a8a8cbb105be87 Mon Sep 17 00:00:00 2001
From: chrchr-github <78114321+chrchr-github@users.noreply.github.com>
Date: Wed, 9 Mar 2022 18:22:30 +0100
Subject: [PATCH] Partial fix for #10848 FP: unusedStructMember (II) (#3881)

* Preliminary

* Fix member search, add tests
---
 lib/symboldatabase.cpp | 44 +++++++++++++++++++++++------------
 test/testunusedvar.cpp | 52 ++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 80 insertions(+), 16 deletions(-)

diff --git a/lib/symboldatabase.cpp b/lib/symboldatabase.cpp
index 568f0e009..bd1fc07ff 100644
--- a/lib/symboldatabase.cpp
+++ b/lib/symboldatabase.cpp
@@ -1210,20 +1210,36 @@ void SymbolDatabase::createSymbolDatabaseSetVariablePointers()
 
         // Set Token::variable pointer for array member variable
         // Since it doesn't point at a fixed location it doesn't have varid
-        if (tok->variable() != nullptr &&
-            (tok->variable()->typeScope() || tok->variable()->isSmartPointer() || (tok->valueType() && tok->valueType()->type == ValueType::CONTAINER)) &&
-            Token::Match(tok, "%name% [|.")) {
-
-            Token *tok2 = tok->next();
-            // Locate "]"
-            while (tok2 && tok2->str() == "[")
-                tok2 = tok2->link()->next();
-
-            Token *membertok = nullptr;
-            if (Token::Match(tok2, ". %name%"))
-                membertok = tok2->next();
-            else if (Token::Match(tok2, ") . %name%") && tok->strAt(-1) == "(")
-                membertok = tok2->tokAt(2);
+        const bool isVar = tok->variable() && (tok->variable()->typeScope() || tok->variable()->isSmartPointer() || (tok->valueType() && tok->valueType()->type == ValueType::CONTAINER));
+        const bool isArrayAccess = isVar && Token::simpleMatch(tok->astParent(), "[");
+        const bool isDirectAccess = isVar && !isArrayAccess && Token::simpleMatch(tok->astParent(), ".");
+        const bool isDerefAccess = isVar && !isDirectAccess && Token::simpleMatch(tok->astParent(), "*") && Token::simpleMatch(tok->astParent()->astParent(), ".");
+        if (isVar && (isArrayAccess || isDirectAccess || isDerefAccess)) {
+            Token* membertok{};
+            if (isArrayAccess) {
+                membertok = const_cast<Token*>(tok->astParent());
+                while (Token::simpleMatch(membertok, "["))
+                    membertok = membertok->astParent();
+                if (membertok)
+                    membertok = membertok->astOperand2();
+            }
+            else if (isDirectAccess) {
+                membertok = const_cast<Token*>(tok->astParent()->astOperand2());
+                if (membertok == tok) {
+                    Token* gptok = const_cast<Token*>(tok->astParent()->astParent());
+                    if (Token::simpleMatch(gptok, ".")) // chained access
+                        membertok = gptok->astOperand2();
+                    else if (Token::simpleMatch(gptok, "[") && Token::simpleMatch(gptok->astParent(), "."))
+                        membertok = gptok->astParent()->astOperand2();
+                }
+            }
+            else { // isDerefAccess
+                membertok = const_cast<Token*>(tok->astParent());
+                while (Token::simpleMatch(membertok, "*"))
+                    membertok = membertok->astParent();
+                if (membertok)
+                    membertok = membertok->astOperand2();
+            }
 
             if (membertok) {
                 const Variable *var = tok->variable();
diff --git a/test/testunusedvar.cpp b/test/testunusedvar.cpp
index db4cafbad..8b12b73cd 100644
--- a/test/testunusedvar.cpp
+++ b/test/testunusedvar.cpp
@@ -1629,8 +1629,8 @@ private:
         ASSERT_EQUALS("", errout.str());
     }
 
-    void structmember19() { // #10826
-        checkStructMemberUsage("class C {};\n"
+    void structmember19() {
+        checkStructMemberUsage("class C {};\n" // #10826
                                "struct S {\n"
                                "    char* p;\n"
                                "    std::string str;\n"
@@ -1653,6 +1653,54 @@ private:
                       "[test.cpp:4]: (style) struct member 'S::str' is never used.\n"
                       "[test.cpp:5]: (style) struct member 'S::c' is never used.\n",
                       errout.str());
+
+        checkStructMemberUsage("struct S {\n"
+                               "    struct T {\n"
+                               "        int i;\n"
+                               "    } t[2];\n"
+                               "};\n"
+                               "S s[1];\n"
+                               "int f() {\n"
+                               "    return s[0].t[1].i;\n"
+                               "}\n");
+        ASSERT_EQUALS("", errout.str());
+
+        checkStructMemberUsage("struct S { int a; };\n"
+                               "struct T { S s; };\n"
+                               "int f(const T** tp) {\n"
+                               "    return tp[0]->s.a;\n"
+                               "}\n");
+        ASSERT_EQUALS("", errout.str());
+
+        checkStructMemberUsage("struct S { int a; };\n"
+                               "int f(const S* sp) {\n"
+                               "    return (*sp).a; \n"
+                               "}\n");
+        ASSERT_EQUALS("", errout.str());
+
+        checkStructMemberUsage("struct S { int a; };\n"
+                               "int f(const S** spp) {\n"
+                               "    return spp[0]->a;\n"
+                               "}\n");
+        ASSERT_EQUALS("", errout.str());
+
+        checkStructMemberUsage("struct S { int a; };\n"
+                               "int f(const S** spp) {\n"
+                               "    return spp[0][0].a;\n"
+                               "}\n");
+        ASSERT_EQUALS("", errout.str());
+
+        checkStructMemberUsage("struct S { int a; };\n"
+                               "int f(const S* sp) {\n"
+                               "    return sp[0].a;\n"
+                               "}\n");
+        ASSERT_EQUALS("", errout.str());
+
+        checkStructMemberUsage("struct S { int a; };\n"
+                               "int f(const S* sp) {\n"
+                               "    return sp->a;\n"
+                               "}\n");
+        ASSERT_EQUALS("", errout.str());
     }
 
     void functionVariableUsage_(const char* file, int line, const char code[], const char filename[] = "test.cpp") {