DLL-Export data in libmatc on Windows.

For data to be exported from a DLL on Windows, it has to be marked with
a `dllexport` attribute. For users of the DLL, the same symbol has to be
marked with a `dllimport` attribute.

Do that with `listheaders` in libmatc to avoid linker errors like the
following for ElmerGUI:
```
D:/a/_temp/msys64/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/14.2.0/../../../../x86_64-w64-mingw32/bin/ld.exe: ElmerGUI/Application/CMakeFiles/ElmerGUI.dir/vtkpost/matc.cpp.obj:matc.cpp:(.rdata$.refptr.listheaders[.refptr.listheaders]+0x0): undefined reference to `listheaders'
```

ElmerGUI/matc/CMakeLists.txt

@@ -5,6 +5,13 @@ FILE(GLOB SOURCES "src/*.c")
 
 IF(NOT(WITH_ELMERGUI))
   ADD_LIBRARY(matc ${SOURCES})
+  IF(${BUILD_SHARED_LIBS})
+    target_compile_definitions(matc PRIVATE BUILD_MATC_DLL)
+    set_target_properties(matc PROPERTIES
+      WINDOWS_EXPORT_ALL_SYMBOLS ON)
+  ELSE()
+    target_compile_definitions(matc PUBLIC MATC_STATIC)
+  ENDIF()
   INSTALL(TARGETS matc RUNTIME DESTINATION "bin" LIBRARY DESTINATION "lib"
     ARCHIVE DESTINATION "lib" COMPONENT "elmergui")
 ENDIF()

ElmerGUI/matc/src/elmer/matc.h

@@ -6,7 +6,7 @@
 
 
 /*
- * $Id: matc.h,v 1.2 2007/06/08 08:12:19 jpr Exp $ 
+ * $Id: matc.h,v 1.2 2007/06/08 08:12:19 jpr Exp $
  *
  * $Log: matc.h,v $
  * Revision 1.2  2007/06/08 08:12:19  jpr
@@ -24,7 +24,7 @@
  * Revision 1.2  1998/08/01 12:34:49  jpr
  *
  * Added Id, started Log.
- * 
+ *
  *
  */
 
@@ -46,6 +46,28 @@
 #define EXT extern
 #endif
 
+#if !defined (_WIN32) || defined (MATC_STATIC)
+#  define MATC_API
+#elseif defined (_WIN32)
+#  if defined (BUILD_MATC_DLL)
+#    if defined (__GNUC__)
+       /* GCC */
+#      define MATC_API __attribute__ ((dllexport))
+#    else
+       /* MSVC */
+#      define MATC_API __declspec(dllexport)
+#    endif
+#  else
+#    if defined (__GNUC__)
+       /* GCC */
+#      define MATC_API __attribute__ ((dllimport))
+#    else
+       /* MSVC */
+#      define MATC_API __declspec(dllimport)
+#    endif
+#  endif
+#endif
+
 /*******************************************************************
                  LIST HANDLING DEFINITIONS
 *******************************************************************/
@@ -60,22 +82,22 @@ typedef struct list {
 */
 #ifdef MODULE_MATC
 
-  EXT LIST listheaders[5] = {
+  MATC_API EXT LIST listheaders[5] = {
     {
       NULL, "Allocations"                    /* memory allocations     */
     }, {
-      NULL, "Constants"                     /* global CONSTANTS        */
+      NULL, "Constants"                      /* global CONSTANTS       */
     }, {
       NULL, "Currently defined VARIABLES"    /* global VARIABLES       */
-    }, { 
+    }, {
       NULL, "Builtin Functions"              /* internal commands      */
     }, {
       NULL, "User Functions"                 /* user defined functions */
     }
   };
 #else
 
-  EXT LIST listheaders[];
+  MATC_API EXT LIST listheaders[];
 
 #endif
 
@@ -182,7 +204,7 @@ typedef struct command
 #define COMSIZE sizeof(COMMAND)
 
 #define CMDFLAG_PW 1           /* element by element operation    */
-#define CMDFLAG_CE 2           /* command can be executed when 
+#define CMDFLAG_CE 2           /* command can be executed when
                                   preprocessing if constant
                                   arguments.                      */
 
@@ -211,7 +233,7 @@ typedef struct function
 typedef enum symbols {
   nullsym,  leftpar,  rightpar, indopen, indclose, power, times, ptimes, divide,
   plus, minus, reduction,  transpose, eq, neq, lt, gt, le, ge, and, or, not,
-  assignsym, apply, resize, vector, statemend, argsep, name, number, string, 
+  assignsym, apply, resize, vector, statemend, argsep, name, number, string,
   funcsym, import, export, ifsym, thensym, elsesym, whilesym, forsym,
   beginsym, endsym, breaksym, comment, systemcall
 } SYMTYPE;
@@ -236,7 +258,7 @@ char csymbols[] = {
 /*--------------------------------------------------------------------*/
 
 char *reswords[] = {
-  "function", "import", "export", "if", "then", "else", "while", "for", 
+  "function", "import", "export", "if", "then", "else", "while", "for",
   "begin", "end", "break", NULL
 };
 
@@ -370,7 +392,7 @@ typedef struct clause
 
 EXT FILE *math_in, *math_out, *math_err;
 
-/* 
+/*
      see doread(), error() in matc.c
 */
 EXT jmp_buf *jmpbuf;
@@ -379,8 +401,8 @@ EXT int term;
 
 #ifdef VAX
 struct desc
-{ 
-  int length; 
+{
+  int length;
   char *addr;
 } ;
 #endif
@@ -409,7 +431,7 @@ void error( char *format, ... )
     va_start( args, format );
 #ifdef STRING_OUTPUT
     if ( math_out_count+512 > math_out_allocated )
-    { 
+    {
         math_out_allocated += 512;
         math_out_str = (char *)realloc( math_out_str, math_out_allocated );
     }
@@ -433,7 +455,7 @@ void PrintOut( char *format, ... )
     va_start( args, format );
 #ifdef STRING_OUTPUT
     if ( math_out_count+512 > math_out_allocated )
-    { 
+    {
         math_out_allocated += 512;
         math_out_str = (char *)realloc( math_out_str, math_out_allocated );
     }
@@ -449,11 +471,11 @@ extern void PrintOut( char *format, ... );
 #endif
 
 /*******************************************************************
-                       function prototypes 
-*******************************************************************/ 
+                       function prototypes
+*******************************************************************/
 #include "fnames.h"
 
 /*******************************************************************
                   graphics package definitions
-*******************************************************************/ 
+*******************************************************************/
 #include "gra.h"