Fixed zerodiv FN for '1/std::erfc(42)'

cfg/std.cfg

@@ -1291,7 +1291,7 @@
   <function name="erfc,std::erfc">
     <use-retval/>
     <pure/>
-    <returnValue type="double"/>
+    <returnValue type="double">erfc(arg1)</returnValue>
     <noreturn>false</noreturn>
     <leak-ignore/>
     <arg nr="1" direction="in">
@@ -1302,7 +1302,7 @@
   <function name="erfcf,std::erfcf">
     <use-retval/>
     <pure/>
-    <returnValue type="float"/>
+    <returnValue type="float">erfc(arg1)</returnValue>
     <noreturn>false</noreturn>
     <leak-ignore/>
     <arg nr="1" direction="in">
@@ -1313,7 +1313,7 @@
   <function name="erfcl,std::erfcl">
     <use-retval/>
     <pure/>
-    <returnValue type="long double"/>
+    <returnValue type="long double">erfc(arg1)</returnValue>
     <noreturn>false</noreturn>
     <leak-ignore/>
     <arg nr="1" direction="in">

lib/programmemory.cpp

@@ -730,6 +730,17 @@ static std::unordered_map<std::string, BuiltinLibraryFunction> createBuiltinLibr
         v.valueType = ValueFlow::Value::ValueType::FLOAT;
         return v;
     };
+    functions["erfc"] = [](const std::vector<ValueFlow::Value>& args) {
+        if (args.size() != 1)
+            return ValueFlow::Value::unknown();
+        ValueFlow::Value v = args[0];
+        if (!v.isFloatValue() && !v.isIntValue())
+            return ValueFlow::Value::unknown();
+        double value = args[0].isFloatValue() ? args[0].floatValue : args[0].intvalue;
+        v.floatValue = std::erfc(value);
+        v.valueType = ValueFlow::Value::ValueType::FLOAT;
+        return v;
+    };
     functions["sqrt"] = [](const std::vector<ValueFlow::Value>& args) {
         if (args.size() != 1)
             return ValueFlow::Value::unknown();

test/cfg/std.cpp

@@ -64,6 +64,13 @@ int zerodiv_erf()
     return 42 / i;
 }
 
+int zerodiv_erfc()
+{
+    int i = std::erfc(42);
+    // cppcheck-suppress zerodiv
+    return 42 / i;
+}
+
 int zerodiv_asin()
 {
     int i = std::asin(0);