ENH: Support preprocessor def values in VS6

The add_definitions() command and COMPILE_DEFINITIONS dir/tgt/src
properties support preprocessor definitions with values.  Previously
values were not supported in the VS6 generator even though the native
tool supports them.  It is only values with spaces that VS6 does not
support.  This enables support and instead complains only for values
with spaces.  See issue #8779.

Source/cmLocalVisualStudio6Generator.cxx

@@ -1712,11 +1712,11 @@ cmLocalVisualStudio6Generator
     }
 
   // Now do the VS6-specific check.
-  if(define.find_first_of("=") != define.npos)
+  if(define.find_first_of(" ") != define.npos)
     {
     cmOStringStream e;
-    e << "WARNING: The VS6 IDE does not support preprocessor definitions "
-      << "with values.\n"
+    e << "WARNING: The VS6 IDE does not support preprocessor definition "
+      << "values with spaces.\n"
       << "CMake is dropping a preprocessor definition: " << define << "\n"
       << "Consider defining the macro in a (configured) header file.\n";
     cmSystemTools::Message(e.str().c_str());

Source/cmMakefile.cxx

@@ -1216,10 +1216,10 @@ bool cmMakefile::ParseDefineFlag(std::string const& def, bool remove)
     return false;
     }
 
-  // VS6 IDE does not support definitions with values.
+  // VS6 IDE does not support definition values with spaces.
   if((strcmp(this->LocalGenerator->GetGlobalGenerator()->GetName(),
              "Visual Studio 6") == 0) &&
-     (def.find("=") != def.npos))
+     (def.find(" ") != def.npos))
     {
     return false;
     }
@@ -3475,7 +3475,7 @@ void cmMakefile::DefineProperties(cmake *cm)
      "in the directory's parent.\n"
      "CMake will automatically drop some definitions that "
      "are not supported by the native build tool.  "
-     "The VS6 IDE does not support definitions with values "
+     "The VS6 IDE does not support definition values with spaces "
      "(but NMake does).\n"
      "Dislaimer: Most native build tools have poor support for escaping "
      "certain values.  CMake has work-arounds for many cases but some "

Source/cmSourceFile.cxx

@@ -405,7 +405,7 @@ void cmSourceFile::DefineProperties(cmake *cm)
      "(ex. \"COMPILE_DEFINITIONS_DEBUG\").\n"
      "CMake will automatically drop some definitions that "
      "are not supported by the native build tool.  "
-     "The VS6 IDE does not support definitions with values "
+     "The VS6 IDE does not support definition values with spaces "
      "(but NMake does).  Xcode does not support per-configuration "
      "definitions on source files.\n"
      "Dislaimer: Most native build tools have poor support for escaping "

Source/cmTarget.cxx

@@ -108,7 +108,7 @@ void cmTarget::DefineProperties(cmake *cm)
      "(ex. \"COMPILE_DEFINITIONS_DEBUG\").\n"
      "CMake will automatically drop some definitions that "
      "are not supported by the native build tool.  "
-     "The VS6 IDE does not support definitions with values "
+     "The VS6 IDE does not support definition values with spaces "
      "(but NMake does).\n"
      "Dislaimer: Most native build tools have poor support for escaping "
      "certain values.  CMake has work-arounds for many cases but some "

Tests/Preprocess/CMakeLists.txt

@@ -65,14 +65,20 @@ if(NOT BORLAND AND NOT PP_VS70)
   set(SEMICOLON "\;")
 endif(NOT BORLAND AND NOT PP_VS70)
 
-if(NOT PP_BORLAND AND NOT PP_WATCOM)
-  # Borland, WMake: multiple spaces
-  # The make tool seems to remove extra whitespace from inside
-  # quoted strings when passing to the compiler.  It does not have
-  # trouble passing to other tools, and the compiler may be directly
-  # invoked from the command line.
-  set(STRING_EXTRA "${STRING_EXTRA}  ")
-endif(NOT PP_BORLAND AND NOT PP_WATCOM)
+if(NOT PP_VS6)
+  # VS 6 IDE: spaces
+  # The project parser unconditionally separates arguments at spaces.
+  set(STRING_EXTRA "${STRING_EXTRA} ")
+
+  if(NOT PP_BORLAND AND NOT PP_WATCOM)
+    # Borland, WMake: multiple spaces
+    # The make tool seems to remove extra whitespace from inside
+    # quoted strings when passing to the compiler.  It does not have
+    # trouble passing to other tools, and the compiler may be directly
+    # invoked from the command line.
+    set(STRING_EXTRA "${STRING_EXTRA} ")
+  endif(NOT PP_BORLAND AND NOT PP_WATCOM)
+endif(NOT PP_VS6)
 
 if(NOT PP_VS)
   # VS: ,
@@ -152,7 +158,7 @@ endif(PP_NMAKE OR PP_UMAKE)
 # support it and it is not an operator it is not worthwhile.
 
 # Compose the final test string.
-set(STRING_VALUE "hello `~!@$*)(_+-=}{][:'.?/ ${STRING_EXTRA}world")
+set(STRING_VALUE "hello`~!@$*)(_+-=}{][:'.?/${STRING_EXTRA}world")
 
 #-----------------------------------------------------------------------------
 # Function-style macro command-line support:
@@ -194,11 +200,7 @@ endif(PP_VS6)
 add_definitions(-DOLD_DEF -DOLD_EXPR=2)
 
 # Make sure old-style definitions are converted to directory property.
-if(PREPROCESS_VS6)
-  set(OLD_DEFS_EXPECTED "OLD_DEF")
-else(PREPROCESS_VS6)
-  set(OLD_DEFS_EXPECTED "OLD_DEF;OLD_EXPR=2")
-endif(PREPROCESS_VS6)
+set(OLD_DEFS_EXPECTED "OLD_DEF;OLD_EXPR=2")
 get_property(OLD_DEFS DIRECTORY PROPERTY COMPILE_DEFINITIONS)
 if(NOT "${OLD_DEFS}" STREQUAL "${OLD_DEFS_EXPECTED}")
   message(SEND_ERROR "add_definitions not converted to directory property!")
@@ -225,23 +227,26 @@ foreach(c "" "_DEBUG" "_RELEASE")
     )
 endforeach(c)
 
-# Add definitions with values.  VS6 does not support this.
+# Add definitions with values.
 if(NOT PREPROCESS_VS6)
-  set_property(
-    TARGET Preprocess
-    APPEND PROPERTY COMPILE_DEFINITIONS
-    "TARGET_STRING=\"${STRING_VALUE}${SEMICOLON}\""
-    "TARGET_EXPR=${EXPR}"
-    "TARGET_PATH=\"${TARGET_PATH}\""
-    )
-  set_property(
-    SOURCE preprocess.c preprocess${VS6}.cxx
-    APPEND PROPERTY COMPILE_DEFINITIONS
-    "FILE_STRING=\"${STRING_VALUE}${SEMICOLON}\""
-    "FILE_EXPR=${EXPR}"
-    "FILE_PATH=\"${FILE_PATH}\""
-    )
+  # The path might have spaces, which VS6 does not support.
+  set(DEF_TARGET_PATH "TARGET_PATH=\"${TARGET_PATH}\"")
+  set(DEF_FILE_PATH "FILE_PATH=\"${FILE_PATH}\"")
 endif(NOT PREPROCESS_VS6)
+set_property(
+  TARGET Preprocess
+  APPEND PROPERTY COMPILE_DEFINITIONS
+  "TARGET_STRING=\"${STRING_VALUE}${SEMICOLON}\""
+  "TARGET_EXPR=${EXPR}"
+  ${DEF_TARGET_PATH}
+  )
+set_property(
+  SOURCE preprocess.c preprocess${VS6}.cxx
+  APPEND PROPERTY COMPILE_DEFINITIONS
+  "FILE_STRING=\"${STRING_VALUE}${SEMICOLON}\""
+  "FILE_EXPR=${EXPR}"
+  ${DEF_FILE_PATH}
+  )
 
 # Helper target for running test manually in build tree.
 add_custom_target(drive COMMAND Preprocess)

Tests/Preprocess/preprocess.c

@@ -9,7 +9,6 @@
 int check_defines_C(void)
 {
   int result = 1;
-#ifndef PREPROCESS_VS6
   if(strcmp(FILE_STRING, STRING_VALUE) != 0)
     {
     fprintf(stderr,
@@ -38,7 +37,6 @@ int check_defines_C(void)
     result = 0;
     }
   }
-#endif
 #ifdef NDEBUG
 # ifdef FILE_DEF_DEBUG
   {

Tests/Preprocess/preprocess.cxx

@@ -11,7 +11,6 @@ extern "C" int check_defines_C(void);
 int check_defines_CXX()
 {
   int result = 1;
-#ifndef PREPROCESS_VS6
   if(strcmp(FILE_STRING, STRING_VALUE) != 0)
     {
     fprintf(stderr,
@@ -40,7 +39,6 @@ int check_defines_CXX()
     result = 0;
     }
   }
-#endif
 #ifdef NDEBUG
 # ifdef FILE_DEF_DEBUG
   {