From cdaa1c30a60817df05ef0415c668c8d6a5b44d29 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludvig=20Gunne=20Lindstr=C3=B6m?=
 <ludviggunnelindstrom@gmail.com>
Date: Tue, 26 Nov 2024 11:43:40 +0100
Subject: [PATCH 1/4] fix #13345

---
 lib/checkunusedvar.cpp | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/lib/checkunusedvar.cpp b/lib/checkunusedvar.cpp
index 755b77517c7..f24e10106d5 100644
--- a/lib/checkunusedvar.cpp
+++ b/lib/checkunusedvar.cpp
@@ -1549,6 +1549,19 @@ void CheckUnusedVar::checkStructMemberUsage()
                     use = true;
                     break;
                 }
+                // Member referenced in offsetof
+                if (Token::Match(tok, ("offsetof ( struct| " + scope.className + " , %name%").c_str())) {
+                    tok = tok->astSibling();
+                    if (!tok)
+                        continue;
+                    tok = tok->astOperand2();
+                    if (!tok)
+                        continue;
+                    if (tok->str() == var.name()) {
+                        use = true;
+                        break;
+                    }
+                }
                 if (tok->variable() != &var)
                     continue;
                 if (tok != var.nameToken()) {

From c12f7f7e45a0fe5dfb3a4b06b9be914764aaad08 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludvig=20Gunne=20Lindstr=C3=B6m?=
 <ludviggunnelindstrom@gmail.com>
Date: Tue, 26 Nov 2024 11:48:09 +0100
Subject: [PATCH 2/4] add test

---
 test/testunusedvar.cpp | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/test/testunusedvar.cpp b/test/testunusedvar.cpp
index 3d57b789c02..d14c791d748 100644
--- a/test/testunusedvar.cpp
+++ b/test/testunusedvar.cpp
@@ -70,6 +70,7 @@ class TestUnusedVar : public TestFixture {
         TEST_CASE(structmember23);
         TEST_CASE(structmember24); // #10847
         TEST_CASE(structmember25);
+        TEST_CASE(structmember26); // #13345
         TEST_CASE(structmember_macro);
         TEST_CASE(classmember);
 
@@ -1962,6 +1963,15 @@ class TestUnusedVar : public TestFixture {
                       errout_str());
     }
 
+    void structmember26() { // #13345
+        checkStructMemberUsage("struct foobar {\n"
+                               "   char unused;\n"
+                               "};\n"
+                               "size_t offset_unused = offsetof(struct foobar, unused);\n");
+        ASSERT_EQUALS("", errout_str());
+
+    }
+
     void structmember_macro() {
         checkStructMemberUsageP("#define S(n) struct n { int a, b, c; };\n"
                                 "S(unused);\n");

From 364fa6a2ea006a3d7e57ed7cb96699f869aabc66 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludvig=20Gunne=20Lindstr=C3=B6m?=
 <ludviggunnelindstrom@gmail.com>
Date: Tue, 26 Nov 2024 11:57:22 +0100
Subject: [PATCH 3/4] remove redundant null checks

---
 lib/checkunusedvar.cpp | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/lib/checkunusedvar.cpp b/lib/checkunusedvar.cpp
index f24e10106d5..fd7fbfc8604 100644
--- a/lib/checkunusedvar.cpp
+++ b/lib/checkunusedvar.cpp
@@ -1551,12 +1551,7 @@ void CheckUnusedVar::checkStructMemberUsage()
                 }
                 // Member referenced in offsetof
                 if (Token::Match(tok, ("offsetof ( struct| " + scope.className + " , %name%").c_str())) {
-                    tok = tok->astSibling();
-                    if (!tok)
-                        continue;
-                    tok = tok->astOperand2();
-                    if (!tok)
-                        continue;
+                    tok = tok->astSibling()->astOperand2();
                     if (tok->str() == var.name()) {
                         use = true;
                         break;

From 3dab3dc63667279fd3d743c25c0f04e1d1c59000 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludvig=20Gunne=20Lindstr=C3=B6m?=
 <ludviggunnelindstrom@gmail.com>
Date: Tue, 26 Nov 2024 11:57:56 +0100
Subject: [PATCH 4/4] remove newline in test

---
 test/testunusedvar.cpp | 1 -
 1 file changed, 1 deletion(-)

diff --git a/test/testunusedvar.cpp b/test/testunusedvar.cpp
index d14c791d748..88a6f0ed0e5 100644
--- a/test/testunusedvar.cpp
+++ b/test/testunusedvar.cpp
@@ -1969,7 +1969,6 @@ class TestUnusedVar : public TestFixture {
                                "};\n"
                                "size_t offset_unused = offsetof(struct foobar, unused);\n");
         ASSERT_EQUALS("", errout_str());
-
     }
 
     void structmember_macro() {