From 0d72216cca6fcbf30b366eb385ecb349994718f9 Mon Sep 17 00:00:00 2001
From: chrchr-github <78114321+chrchr-github@users.noreply.github.com>
Date: Fri, 22 Jul 2022 07:24:34 +0200
Subject: [PATCH] Fix BufferOverrun TODO (#4300)

* Fix BufferOverrun TODO

* clang-tidy
---
 lib/checkbufferoverrun.cpp | 15 +++++++++++++++
 test/testbufferoverrun.cpp |  8 +++++++-
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/lib/checkbufferoverrun.cpp b/lib/checkbufferoverrun.cpp
index 68b42a1d1..51ac7ba48 100644
--- a/lib/checkbufferoverrun.cpp
+++ b/lib/checkbufferoverrun.cpp
@@ -318,6 +318,21 @@ void CheckBufferOverrun::arrayIndex()
         if (!getDimensionsEtc(tok->astOperand1(), mSettings, &dimensions, &errorPath, &mightBeLarger, &path))
             continue;
 
+        const Variable* const var = array->variable();
+        if (var && var->isArgument() && var->scope()) {
+            const Token* changeTok = var->scope()->bodyStart;
+            bool isChanged = false;
+            while ((changeTok = findVariableChanged(changeTok->next(), var->scope()->bodyEnd, /*indirect*/ 0, var->declarationId(),
+                                                    /*globalvar*/ false, mSettings, mTokenizer->isCPP()))) {
+                if (!Token::simpleMatch(changeTok->astParent(), "[")) {
+                    isChanged = true;
+                    break;
+                }
+            }
+            if (isChanged)
+                continue;
+        }
+
         // Positive index
         if (!mightBeLarger) { // TODO check arrays with dim 1 also
             const std::vector<ValueFlow::Value>& indexValues =
diff --git a/test/testbufferoverrun.cpp b/test/testbufferoverrun.cpp
index 7a0d88461..c2cc7b6f2 100644
--- a/test/testbufferoverrun.cpp
+++ b/test/testbufferoverrun.cpp
@@ -2641,7 +2641,13 @@ private:
               "  a += 4;\n"
               "  a[-1] = 0;\n"
               "}");
-        TODO_ASSERT_EQUALS("", "[test.cpp:3]: (error) Array 'a[10]' accessed at index -1, which is out of bounds.\n", errout.str());
+        ASSERT_EQUALS("", errout.str());
+
+        check("void f(char a[10]) {\n"
+              "  a[0] = 0;\n"
+              "  a[-1] = 0;\n"
+              "}");
+        ASSERT_EQUALS("[test.cpp:3]: (error) Array 'a[10]' accessed at index -1, which is out of bounds.\n", errout.str());
     }
 
     void array_index_enum_array() { // #8439