In a header file of your C/C++ application or extension that includes the Tcl library, add these lines:
#include <tcl.h>
...
#if ((TCL_MAJOR_VERSION < 8) || ((TCL_MAJOR_VERSION == 8) \
&& (TCL_MINOR_VERSION == 0)))
extern char * Tcl_PkgPresent _ANSI_ARGS_((Tcl_Interp *, char *, char *, int));
#endifSomewhere in your program/library code, add these lines:
#if ((TCL_MAJOR_VERSION < 8) || ((TCL_MAJOR_VERSION == 8) \
&& (TCL_MINOR_VERSION == 0)))
char *
Tcl_PkgPresent(Tcl_Interp* interp, char* name, char* version, int exact)
{
/*
Must use writable buffer to support Tcl 7.
The Tcl_DStringAppend interface became CONST in Tcl 8
*/
char *cmd = "package provide";
Tcl_DString buf;
Tcl_DString loadedVersion;
/*
Use [package provide] to query if the named package is
already in the interpreter. Tcl_PkgProvide() doesn't
return the version, so a Tcl_Eval() is necessary.
*/
Tcl_DStringInit(&buf);
Tcl_DStringAppend(&buf, cmd, -1);
Tcl_Eval(interp, Tcl_DStringAppendElement(&buf, name));
Tcl_DStringFree(&buf);
Tcl_DStringInit(&loadedVersion);
Tcl_DStringGetResult(interp, &loadedVersion);
if ( !(Tcl_DStringLength(&loadedVersion)) ) {
Tcl_DStringFree(&loadedVersion);
if (version != NULL) {
Tcl_AppendResult(interp, "package ", name, " ", version,
" is not present", (char *) NULL);
} else {
Tcl_AppendResult(interp, "package ", name,
" is not present", (char *) NULL);
}
return NULL;
}
Tcl_DStringFree(&loadedVersion);
/*
At this point we know some version is loaded, so
Tcl_PkgRequire will have no side effect. Call it
to do the rest of the work.
*/
return Tcl_PkgRequire(interp, name, version, exact);
}
#endifThere! Now you can call Tcl_PkgPresent() even if you happen to link against a pre-Tcl 8.1 library.
