[fix] csubstr::compare(char): refactor to avoid warning from VS2022

changelog/current.md

@@ -14,3 +14,4 @@
   - Always use the fastest implementation available: `std::from_chars()` if available (C++17 or higher standard, with later compilers), `fast_float::from_chars()` otherwise. On Visual Studio, `fast_float::from_chars()` is preferred over `std::from_chars()`.
   - If `std::from_chars()` is not available and `C4CORE_NO_FAST_FLOAT` is defined, then the fallback is based on `sscanf()`.
   - Ensure hexadecimal floats are accepted. The current fast_float implementation does not accept hexadecimal floats, so an hexfloat scanner was added.
+- Fix [#84](https://github.com/biojppm/c4core/issues/84): `csubstr::compare(char)`: refactor to avoid false-positive warning from VS2022.

src/c4/substr.hpp

@@ -223,11 +223,10 @@ struct C4CORE_EXPORT basic_substring
     int compare(C const c) const
     {
         C4_XASSERT((str != nullptr) || len == 0);
-        if( ! len)
+        if(C4_LIKELY(str != nullptr && len > 0))
+            return (*str != c) ? *str - c : (static_cast<int>(len) - 1);
+        else
             return -1;
-        if(*str == c)
-            return static_cast<int>(len - 1);
-        return *str - c;
     }
 
     int compare(const char *that, size_t sz) const
@@ -241,7 +240,7 @@ struct C4CORE_EXPORT basic_substring
                 ret = len < sz ? -1 : 1;
             return ret;
         }
-        if((!str && !that) || (len == sz))
+        else if((!str && !that) || (len == sz))
         {
             C4_XASSERT(len == 0 && sz == 0);
             return 0;

test/test_substr.cpp

@@ -1048,6 +1048,10 @@ TEST_CASE("substr.compare_null")
 
 TEST_CASE("substr.compare_vs_char")
 {
+    CHECK_EQ(csubstr().compare('1'), -1); // str==null, len==0
+    CHECK_EQ(csubstr("0123").first(0).compare('1'), -1); // str!=null, len==0
+    CHECK_EQ(csubstr("0123").first(1).compare('1'), -1);
+
     CHECK_EQ(csubstr("-"), '-');
     CHECK_NE(csubstr("+"), '-');