Use CMake to test for strncasecmp

CMakeLists.txt

@@ -15,6 +15,7 @@ project("${ID_PROJECT_NAME}"
     HOMEPAGE_URL "https://LegalizeAdulthood.github.io/iterated-dynamics"
     LANGUAGES CXX)
 
+include(CheckSymbolExists)
 include(CTest)
 include(TestBigEndian)
 
@@ -62,10 +63,12 @@ add_subdirectory(win32)
 add_subdirectory(hc)
 
 test_big_endian(ID_BIG_ENDIAN)
+check_symbol_exists(strncasecmp "strings.h" ID_HAVE_STRNCASECMP)
 configure_file(headers/port_config.h.in include/port_config.h)
 add_library(config INTERFACE)
 target_sources(config INTERFACE
     headers/port_config.h.in
+    headers/string_case_compare.h
     "${CMAKE_CURRENT_BINARY_DIR}/include/port_config.h"
 )
 target_include_directories(config INTERFACE "${CMAKE_CURRENT_BINARY_DIR}/include")

common/realdos.cpp

@@ -17,6 +17,7 @@
 #include "prompts2.h"
 #include "realdos.h"
 #include "rotate.h"
+#include "string_case_compare.h"
 #include "zoom.h"
 
 #include <cassert>

headers/port_config.h.in

@@ -1,3 +1,5 @@
 #pragma once
 
 #cmakedefine01 ID_BIG_ENDIAN
+
+#cmakedefine ID_HAVE_STRNCASECMP

headers/string_case_compare.h

@@ -0,0 +1,22 @@
+#pragma once
+
+#ifdef ID_HAVE_STRNCASECMP
+#include <strings.h>
+
+#else
+#include <cctype>
+
+// case independent version of std::strncmp
+inline int strncasecmp(char const *s, char const *t, int ct)
+{
+    for (; (std::tolower(*s) == std::tolower(*t)) && --ct ; s++, t++)
+    {
+        if (*s == '\0')
+        {
+            return 0;
+        }
+    }
+    return std::tolower(*s) - std::tolower(*t);
+}
+
+#endif

win32/os_win32.cpp

@@ -816,16 +816,3 @@ void init_failure(char const *message)
 {
     MessageBox(nullptr, message, "FractInt: Fatal Error", MB_OK);
 }
-
-// case independent version of std::strncmp
-int strncasecmp(char const *s, char const *t, int ct)
-{
-    for (; (std::tolower(*s) == std::tolower(*t)) && --ct ; s++, t++)
-    {
-        if (*s == '\0')
-        {
-            return 0;
-        }
-    }
-    return std::tolower(*s) - std::tolower(*t);
-}