From ad068daf677eb1f2cb7ffdb9eb0fe6985e7afa70 Mon Sep 17 00:00:00 2001
From: chrchr-github <78114321+chrchr-github@users.noreply.github.com>
Date: Fri, 20 Mar 2026 15:03:12 +0100
Subject: [PATCH 1/3] Update testunusedvar.cpp

---
 test/testunusedvar.cpp | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/test/testunusedvar.cpp b/test/testunusedvar.cpp
index e5f4c08f043..75fe4e85e1d 100644
--- a/test/testunusedvar.cpp
+++ b/test/testunusedvar.cpp
@@ -5813,6 +5813,22 @@ class TestUnusedVar : public TestFixture {
                               "    {}\n"
                               "}");
         ASSERT_EQUALS("", errout_str());
+
+        functionVariableUsage("void f(const int* b, int x) {\n" // #11125
+                              "    int a[6];\n"
+                              "    int i = 0;\n"
+                              "    for (int j = 0; j < 6; ++j) {\n"
+                              "        if (b[j] != 0) {\n"
+                              "            a[i] = j;\n"
+                              "            ++i;\n"
+                              "        }\n"
+                              "    }\n"
+                              "    if (i > 1) {\n"
+                              "        a[i] = a[0];\n"
+                              "        (void)a[x];\n"
+                              "    }\n"
+                              "}\n");
+        ASSERT_EQUALS("", errout_str());
     }
 
     void localvarForEach() { // #4155 - foreach

From e6476f24ecaa99fcabeed9a059e842a5905bc3c8 Mon Sep 17 00:00:00 2001
From: chrchr-github <78114321+chrchr-github@users.noreply.github.com>
Date: Fri, 20 Mar 2026 15:06:43 +0100
Subject: [PATCH 2/3] Update fwdanalysis.cpp

---
 lib/fwdanalysis.cpp | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/lib/fwdanalysis.cpp b/lib/fwdanalysis.cpp
index 6363100b083..9229407c96a 100644
--- a/lib/fwdanalysis.cpp
+++ b/lib/fwdanalysis.cpp
@@ -410,6 +410,14 @@ FwdAnalysis::Result FwdAnalysis::checkRecursive(const Token *expr, const Token *
     return Result(Result::Type::NONE);
 }
 
+static bool isSimpleIndexExpression(const Token* tok)
+{
+    const Token* idx = tok->astOperand2();
+    if (idx->isIncDecOp())
+        idx = idx->astOperand1();
+    return idx->variable() && idx->variable()->scope() == tok->scope();
+}
+
 std::set<nonneg int> FwdAnalysis::getExprVarIds(const Token* expr, bool* localOut, bool* unknownVarIdOut) const
 {
     // all variable ids in expr.
@@ -418,7 +426,7 @@ std::set<nonneg int> FwdAnalysis::getExprVarIds(const Token* expr, bool* localOu
     bool unknownVarId = false;
     visitAstNodes(expr,
                   [&](const Token *tok) {
-        if (tok->str() == "[" && mWhat == What::UnusedValue)
+        if (tok->str() == "[" && mWhat == What::UnusedValue && isSimpleIndexExpression(tok))
             return ChildrenToVisit::op1;
         if (tok->varId() == 0 && tok->isName() && tok->strAt(-1) != ".") {
             // unknown variable

From c62e7d611408ccb9a6d2f78b339c2b5b1a3597e8 Mon Sep 17 00:00:00 2001
From: chrchr-github <78114321+chrchr-github@users.noreply.github.com>
Date: Fri, 20 Mar 2026 16:02:29 +0100
Subject: [PATCH 3/3] Update fwdanalysis.cpp

---
 lib/fwdanalysis.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/fwdanalysis.cpp b/lib/fwdanalysis.cpp
index 9229407c96a..b30b928cfae 100644
--- a/lib/fwdanalysis.cpp
+++ b/lib/fwdanalysis.cpp
@@ -413,6 +413,8 @@ FwdAnalysis::Result FwdAnalysis::checkRecursive(const Token *expr, const Token *
 static bool isSimpleIndexExpression(const Token* tok)
 {
     const Token* idx = tok->astOperand2();
+    if (!idx)
+        return false;
     if (idx->isIncDecOp())
         idx = idx->astOperand1();
     return idx->variable() && idx->variable()->scope() == tok->scope();