From 47c3ad1b7536fe055e53daf9ff6cd4ae500e7a67 Mon Sep 17 00:00:00 2001
From: chrchr-github <78114321+chrchr-github@users.noreply.github.com>
Date: Wed, 31 Jan 2024 20:39:23 +0100
Subject: [PATCH] Partial fix for #12387 FP unsignedLessThanZero for template
 type (#5922)

---
 lib/checkcondition.cpp |  2 +-
 lib/checkother.cpp     |  6 +++++-
 lib/checkother.h       |  2 +-
 test/testother.cpp     | 12 ++++++++++++
 4 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/lib/checkcondition.cpp b/lib/checkcondition.cpp
index f03ed2953a1..0e3fe825a21 100644
--- a/lib/checkcondition.cpp
+++ b/lib/checkcondition.cpp
@@ -1567,7 +1567,7 @@ void CheckCondition::alwaysTrueFalse()
             {
                 const ValueFlow::Value *zeroValue = nullptr;
                 const Token *nonZeroExpr = nullptr;
-                if (CheckOther::comparisonNonZeroExpressionLessThanZero(tok, &zeroValue, &nonZeroExpr) ||
+                if (CheckOther::comparisonNonZeroExpressionLessThanZero(tok, &zeroValue, &nonZeroExpr, /*suppress*/ true) ||
                     CheckOther::testIfNonZeroExpressionIsPositive(tok, &zeroValue, &nonZeroExpr))
                     continue;
             }
diff --git a/lib/checkother.cpp b/lib/checkother.cpp
index fa43aba816a..22a279ed87d 100644
--- a/lib/checkother.cpp
+++ b/lib/checkother.cpp
@@ -2737,7 +2737,7 @@ void CheckOther::checkSignOfUnsignedVariable()
     }
 }
 
-bool CheckOther::comparisonNonZeroExpressionLessThanZero(const Token *tok, const ValueFlow::Value **zeroValue, const Token **nonZeroExpr)
+bool CheckOther::comparisonNonZeroExpressionLessThanZero(const Token *tok, const ValueFlow::Value **zeroValue, const Token **nonZeroExpr, bool suppress)
 {
     if (!tok->isComparisonOp() || !tok->astOperand1() || !tok->astOperand2())
         return false;
@@ -2755,6 +2755,10 @@ bool CheckOther::comparisonNonZeroExpressionLessThanZero(const Token *tok, const
         return false;
     }
 
+    if (const Variable* var = (*nonZeroExpr)->variable())
+        if (var->typeStartToken()->isTemplateArg())
+            return suppress;
+
     const ValueType* vt = (*nonZeroExpr)->valueType();
     return vt && (vt->pointer || vt->sign == ValueType::UNSIGNED);
 }
diff --git a/lib/checkother.h b/lib/checkother.h
index a2f440ccc73..2600bb4f329 100644
--- a/lib/checkother.h
+++ b/lib/checkother.h
@@ -56,7 +56,7 @@ class CPPCHECKLIB CheckOther : public Check {
     CheckOther() : Check(myName()) {}
 
     /** Is expression a comparison that checks if a nonzero (unsigned/pointer) expression is less than zero? */
-    static bool comparisonNonZeroExpressionLessThanZero(const Token *tok, const ValueFlow::Value **zeroValue, const Token **nonZeroExpr);
+    static bool comparisonNonZeroExpressionLessThanZero(const Token *tok, const ValueFlow::Value **zeroValue, const Token **nonZeroExpr, bool suppress = false);
 
     /** Is expression a comparison that checks if a nonzero (unsigned/pointer) expression is positive? */
     static bool testIfNonZeroExpressionIsPositive(const Token *tok, const ValueFlow::Value **zeroValue, const Token **nonZeroExpr);
diff --git a/test/testother.cpp b/test/testother.cpp
index 71a284d499d..2dbebf306d8 100644
--- a/test/testother.cpp
+++ b/test/testother.cpp
@@ -8250,6 +8250,18 @@ class TestOther : public TestFixture {
               "   if (y < x) {}\n"
               "}");
         ASSERT_EQUALS("[test.cpp:4]: (style) Checking if unsigned expression 'y' is less than zero.\n", errout.str());
+
+        // #12387
+        check("template<typename T>\n"
+              "void f(T t) {\n"
+              "    if constexpr (std::numeric_limits<T>::is_signed) {\n"
+              "        if (t < 0) {}\n"
+              "    }\n"
+              "}\n"
+              "void g() {\n"
+              "    f<uint32_t>(0);\n"
+              "}");
+        ASSERT_EQUALS("", errout.str());
     }
 
     void checkSignOfPointer() {