From cae27c5ec770890edf788cbbf82d881b862301ba Mon Sep 17 00:00:00 2001
From: chrchr-github <78114321+chrchr-github@users.noreply.github.com>
Date: Sat, 28 Oct 2023 16:47:57 +0200
Subject: [PATCH] Fix #12117 FP integerOverflowCond for shift by 31 bits
 (#5596)

---
 lib/checktype.cpp | 4 ++--
 test/testtype.cpp | 5 +++++
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/lib/checktype.cpp b/lib/checktype.cpp
index d1c95d20e..f6e029290 100644
--- a/lib/checktype.cpp
+++ b/lib/checktype.cpp
@@ -205,8 +205,8 @@ void CheckType::checkIntegerOverflow()
             continue;
 
         // For left shift, it's common practice to shift into the sign bit
-        //if (tok->str() == "<<" && value->intvalue > 0 && value->intvalue < (((MathLib::bigint)1) << bits))
-        //    continue;
+        if (tok->str() == "<<" && value->intvalue > 0 && value->intvalue < (((MathLib::bigint)1) << bits))
+            continue;
 
         integerOverflowError(tok, *value);
     }
diff --git a/test/testtype.cpp b/test/testtype.cpp
index c2e436876..d15363104 100644
--- a/test/testtype.cpp
+++ b/test/testtype.cpp
@@ -295,6 +295,11 @@ private:
               "   return 123456U * x;\n"
               "}",settings);
         ASSERT_EQUALS("", errout.str());
+
+        check("int f(int i) {\n" // #12117
+              "    return (i == 31) ? 1 << i : 0;\n"
+              "}", settings);
+        ASSERT_EQUALS("[test.cpp:2] -> [test.cpp:2]: (warning) Shifting signed 32-bit value by 31 bits is undefined behaviour. See condition at line 2.\n", errout.str());
     }
 
     void signConversion() {