COMP: Avoid String.c inclusion by Compaq templates

The Compaq compiler (on VMS) includes 'String.c' in source files that
use the stl string while looking for template definitions.  This was the
true cause of double-inclusion of the 'kwsysPrivate.h' header.  We work
around the problem by conditionally compiling the entire source file on
a condition only true when really building the source.

Source/kwsys/CMakeLists.txt

@@ -848,6 +848,12 @@ ENDIF(KWSYS_ENABLE_C AND KWSYS_C_SRCS)
 # line to configure the namespace in the C and C++ source files.
 ADD_DEFINITIONS("-DKWSYS_NAMESPACE=${KWSYS_NAMESPACE}")
 
+IF(KWSYS_USE_String)
+  # Activate code in "String.c".  See the comment in the source.
+  SET_SOURCE_FILES_PROPERTIES(String.c PROPERTIES
+    COMPILE_FLAGS "-DKWSYS_STRING_C")
+ENDIF(KWSYS_USE_String)
+
 #-----------------------------------------------------------------------------
 # Process execution on windows needs to build a forwarding executable
 # that works around a Win9x bug.  We encode the executable into a C

Source/kwsys/String.c

@@ -11,6 +11,14 @@
      PURPOSE.  See the above copyright notices for more information.
 
 =========================================================================*/
+#ifdef KWSYS_STRING_C
+/*
+All code in this source file is conditionally compiled to work-around
+template definition auto-search on VMS.  Other source files in this
+directory that use the stl string cause the compiler to load this
+source to try to get the definition of the string template.  This
+condition blocks the compiler from seeing the symbols defined here.
+*/
 #include "kwsysPrivate.h"
 #include KWSYS_HEADER(String.h)
 
@@ -105,3 +113,5 @@ int kwsysString_strncasecmp(const char* lhs, const char* rhs, size_t n)
   return result;
 #endif
 }
+
+#endif /* KWSYS_STRING_C */

Source/kwsys/kwsysPrivate.h

@@ -39,7 +39,5 @@
 #define KWSYS_NAMESPACE_STRING1(x) #x
 
 #else
-# ifndef __VMS /* Avoid strange false positive on VMS compiler.  */
-#  error "kwsysPrivate.h included multiple times."
-# endif
+# error "kwsysPrivate.h included multiple times."
 #endif

bootstrap

@@ -1286,6 +1286,7 @@ if [ "x${cmake_cxx_flags}" != "x" ]; then
   cmake_cxx_flags="${cmake_cxx_flags} "
 fi
 
+cmake_c_flags_String="-DKWSYS_STRING_C"
 cmake_c_flags="${cmake_c_flags}-I`cmake_escape \"${cmake_source_dir}/Source\"` \
   -I`cmake_escape \"${cmake_bootstrap_dir}\"`"
 cmake_cxx_flags="${cmake_cxx_flags}-I`cmake_escape \"${cmake_source_dir}/Source\"` \
@@ -1305,8 +1306,9 @@ for a in ${CMAKE_C_SOURCES}; do
 done
 for a in ${KWSYS_C_SOURCES} ${KWSYS_C_MINGW_SOURCES}; do
   src=`cmake_escape "${cmake_source_dir}/Source/kwsys/${a}.c"`
+  src_flags=`eval echo \\${cmake_c_flags_\${a}}`
   echo "${a}.o : ${src} ${dep}" >> "${cmake_bootstrap_dir}/Makefile"
-  echo "	${cmake_c_compiler} ${cmake_c_flags} -DKWSYS_NAMESPACE=cmsys -c ${src} -o ${a}.o" >> "${cmake_bootstrap_dir}/Makefile"
+  echo "	${cmake_c_compiler} ${cmake_c_flags} -DKWSYS_NAMESPACE=cmsys ${src_flags} -c ${src} -o ${a}.o" >> "${cmake_bootstrap_dir}/Makefile"
 done
 for a in ${KWSYS_CXX_SOURCES}; do
   src=`cmake_escape "${cmake_source_dir}/Source/kwsys/${a}.cxx"`