Refactor: Add cmSystemTools::GetSystemName()

And use it for CMAKE_HOST_SYSTEM_NAME and CMAKE_SYSTEM_NAME.

Help/release/dev/cmake-system-name-version.rst

@@ -0,0 +1,10 @@
+cmake-system-name-version
+-------------------------
+
+* :variable:`CMAKE_HOST_SYSTEM_NAME`'s undocumented version-stripping behavior
+  has been moved earlier, before :command:`project` or
+  :command:`enable_language` is called.
+* :variable:`CMAKE_SYSTEM_NAME`'s undocumented version-stripping behavior has
+  been removed entirely. If it is set by a ``-D`` flag or by a
+  :manual:`toolchain file <cmake-toolchains(7)>`, it is left unaltered, even if
+  it still contains a version number.

Modules/CMakeDetermineSystem.cmake

@@ -158,38 +158,15 @@ endif()
 
 include(Platform/${CMAKE_SYSTEM_NAME}-Determine OPTIONAL)
 
-macro(ADJUST_CMAKE_SYSTEM_VARIABLES _PREFIX)
-  if(NOT ${_PREFIX}_NAME)
-    set(${_PREFIX}_NAME "UnknownOS")
+set(CMAKE_SYSTEM ${CMAKE_SYSTEM_NAME})
+if(CMAKE_SYSTEM_VERSION)
+  string(APPEND CMAKE_SYSTEM -${CMAKE_SYSTEM_VERSION})
 endif()
-
-  # fix for BSD/OS , remove the /
-  if(${_PREFIX}_NAME MATCHES BSD.OS)
-    set(${_PREFIX}_NAME BSDOS)
+set(CMAKE_HOST_SYSTEM ${CMAKE_HOST_SYSTEM_NAME})
+if(CMAKE_HOST_SYSTEM_VERSION)
+  string(APPEND CMAKE_HOST_SYSTEM -${CMAKE_HOST_SYSTEM_VERSION})
 endif()
 
-  # fix for GNU/kFreeBSD, remove the GNU/
-  if(${_PREFIX}_NAME MATCHES kFreeBSD)
-    set(${_PREFIX}_NAME kFreeBSD)
-  endif()
-
-  # fix for CYGWIN which has windows version in it
-  if(${_PREFIX}_NAME MATCHES CYGWIN)
-    set(${_PREFIX}_NAME CYGWIN)
-  endif()
-
-  # set CMAKE_SYSTEM to the CMAKE_SYSTEM_NAME
-  set(${_PREFIX}  ${${_PREFIX}_NAME})
-  # if there is a CMAKE_SYSTEM_VERSION then add a -${CMAKE_SYSTEM_VERSION}
-  if(${_PREFIX}_VERSION)
-    set(${_PREFIX} ${${_PREFIX}}-${${_PREFIX}_VERSION})
-  endif()
-
-endmacro()
-
-ADJUST_CMAKE_SYSTEM_VARIABLES(CMAKE_SYSTEM)
-ADJUST_CMAKE_SYSTEM_VARIABLES(CMAKE_HOST_SYSTEM)
-
 # this file is also executed from cpack, then we don't need to generate these files
 # in this case there is no CMAKE_BINARY_DIR
 if(CMAKE_BINARY_DIR)

Source/cmStateSnapshot.cxx

@@ -16,15 +16,8 @@
 #include "cmState.h"
 #include "cmStateDirectory.h"
 #include "cmStatePrivate.h"
-#include "cmVersion.h"
-
-#if !defined(_WIN32)
-#  include <sys/utsname.h>
-#endif
-
-#if defined(__CYGWIN__)
 #include "cmSystemTools.h"
-#endif
+#include "cmVersion.h"
 
 cmStateSnapshot::cmStateSnapshot(cmState* state)
   : State(state)
@@ -303,23 +296,15 @@ void cmStateSnapshot::SetDefaultDefinitions()
     working, these variables are still also set here in this place, but they
     will be reset in CMakeSystemSpecificInformation.cmake before the platform
     files are executed. */
-#if defined(_WIN32)
+  cm::string_view hostSystemName = cmSystemTools::GetSystemName();
+  this->SetDefinition("CMAKE_HOST_SYSTEM_NAME", hostSystemName);
+  if (hostSystemName == "Windows") {
     this->SetDefinition("WIN32", "1");
     this->SetDefinition("CMAKE_HOST_WIN32", "1");
-  this->SetDefinition("CMAKE_HOST_SYSTEM_NAME", "Windows");
-#else
+  } else {
     this->SetDefinition("UNIX", "1");
     this->SetDefinition("CMAKE_HOST_UNIX", "1");
-
-#  if defined(__ANDROID__)
-  this->SetDefinition("CMAKE_HOST_SYSTEM_NAME", "Android");
-#  else
-  struct utsname uts_name;
-  if (uname(&uts_name) >= 0) {
-    this->SetDefinition("CMAKE_HOST_SYSTEM_NAME", uts_name.sysname);
   }
-#  endif
-#endif
 #if defined(__CYGWIN__)
   std::string legacy;
   if (cmSystemTools::GetEnv("CMAKE_LEGACY_CYGWIN_WIN32", legacy) &&

Source/cmSystemTools.cxx

@@ -103,6 +103,10 @@
 #  include <malloc.h> /* for malloc/free on QNX */
 #endif
 
+#if !defined(_WIN32) && !defined(__ANDROID__)
+#  include <sys/utsname.h>
+#endif
+
 namespace {
 
 cmSystemTools::InterruptCallback s_InterruptCallback;
@@ -3207,3 +3211,46 @@ bool cmSystemTools::CreateLink(const std::string& origName,
 
   return true;
 }
+
+cm::string_view cmSystemTools::GetSystemName()
+{
+#if defined(_WIN32)
+  return "Windows";
+#elif defined(__ANDROID__)
+  return "Android";
+#else
+  static struct utsname uts_name;
+  static bool initialized = false;
+  static cm::string_view systemName;
+  if (initialized) {
+    return systemName;
+  }
+  if (uname(&uts_name) >= 0) {
+    initialized = true;
+    systemName = uts_name.sysname;
+
+    if (cmIsOff(systemName)) {
+      systemName = "UnknownOS";
+    }
+
+    // fix for BSD/OS, remove the /
+    static const cmsys::RegularExpression bsdOsRegex("BSD.OS");
+    cmsys::RegularExpressionMatch match;
+    if (bsdOsRegex.find(uts_name.sysname, match)) {
+      systemName = "BSDOS";
+    }
+
+    // fix for GNU/kFreeBSD, remove the GNU/
+    if (systemName.find("kFreeBSD") != cm::string_view::npos) {
+      systemName = "kFreeBSD";
+    }
+
+    // fix for CYGWIN which has windows version in it
+    if (systemName.find("CYGWIN") != cm::string_view::npos) {
+      systemName = "CYGWIN";
+    }
+    return systemName;
+  }
+  return "";
+#endif
+}

Source/cmSystemTools.h

@@ -498,6 +498,9 @@ public:
                          const std::string& newName,
                          std::string* errorMessage = nullptr);
 
+  /** Get the system name. */
+  static cm::string_view GetSystemName();
+
 private:
   static bool s_ForceUnixPaths;
   static bool s_RunCommandHideConsole;