From 7d9fdf582b8bc92048e81173b2349ccf7b8d8cac Mon Sep 17 00:00:00 2001
From: Paul Fultz II <pfultz2@yahoo.com>
Date: Sun, 1 Aug 2021 03:10:11 -0500
Subject: [PATCH] Fix 10121: False positive: Condition 'ab->a!=123' is always
 false when modifying an alias (#3293)

---
 lib/valueflow.cpp      |  2 +-
 test/testcondition.cpp | 21 +++++++++++++++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/lib/valueflow.cpp b/lib/valueflow.cpp
index 4c3b8c058..b0e9aad57 100644
--- a/lib/valueflow.cpp
+++ b/lib/valueflow.cpp
@@ -2428,7 +2428,7 @@ struct ExpressionAnalyzer : SingleValueFlowAnalyzer {
             return;
         visitAstNodes(start, [&](const Token* tok) {
             for (const ValueFlow::Value& v : tok->values()) {
-                if (!v.isLocalLifetimeValue())
+                if (!(v.isLocalLifetimeValue() || (astIsPointer(tok) && v.isSymbolicValue() && v.isKnown())))
                     continue;
                 if (!v.tokvalue)
                     continue;
diff --git a/test/testcondition.cpp b/test/testcondition.cpp
index 7bbfbfbd9..4c93dbe2c 100644
--- a/test/testcondition.cpp
+++ b/test/testcondition.cpp
@@ -3642,6 +3642,27 @@ private:
               "}\n");
         ASSERT_EQUALS("", errout.str());
 
+        // #10121
+        check("struct AB {\n"
+              "    int a;\n"
+              "};\n"
+              "struct ABC {\n"
+              "    AB* ab;\n"
+              "};\n"
+              "void g(ABC*);\n"
+              "int f(struct ABC *abc) {\n"
+              "    int err = 0;\n"
+              "    AB *ab = abc->ab;\n"
+              "    if (ab->a == 123){\n"
+              "        g(abc);\n"
+              "        if (ab->a != 123) {\n"
+              "            err = 1;\n"
+              "        }\n"
+              "    }\n"
+              "    return err;\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
+
         // #10323
         check("void foo(int x) {\n"
               "    if(x)\n"