For this definition pulled from a library header file...
typedef struct {
const void *data;
unsigned private_flags;
} CXString;
which is used with a helper function to get a usable string like...
void show_clang_version(void)
{ CXString version = clang_getClangVersion();
printf("%s\n", clang_getCString(version));
clang_disposeString(version);
}
==> 'Debian clang version 3.5.0-10 (tags/RELEASE_350/final) (based on
LLVM 3.5.0)'
So I defined...
FFIExternalStructure subclass: #CXString
instanceVariableNames: ''
classVariableNames: ''
package: 'LibCLang'
and ignoring the const as advised in the manual [1], I try...
CXString class >> fieldsDesc
^ #(
void *data;
unsigned private_flags;
)
but...
CXString rebuildFieldAccessors.
==>Error: Unable to resolve external type: unsigned
I also tried "unsigned int private_flags;"
but get the same error. Any ideas what is wrong?
Actually I can kind of ignore creating accessors since this is like an
opaque type where I'm not expected to access its internals, but I do
need CXString as a return value like this...
LibCLang class >> getClangVersion
^ self ffiCall: #( CXString clang_getClangVersion () ) module: LibCLang
which needs to be passed to this function to get a workable string....
LibCLang class >> getString: aCXString
^ self ffiCall: #( String clang_getCString ( CXString aCXString )
) module: LibCLang
However this doesn't work if I use FFIOpaqueObject instead of
FFIExternalStructure.
I guess the difference is opaque objects are normally pointers to a
type, whereas here that pointer is contained in a struct.
What I've done at the moment to push ahead with experimenting is avoid
needing to generate accessors by adding...
CXString >> printOn: asStream
self getString printOn: aStream
CXString >> getString
^ self ffiCall: #( String clang_getCString ( CXString self ) )
module: LibCLang
such that...
LibCLang getClangVersion "<Print It>"
==> 'Debian clang version 3.5.0-10 (tags/RELEASE_350/final) (based
on LLVM 3.5.0)'
Is there a better way to approach this?
cheers -ben
btw, this is in Pharo 5 (Moose 6).
[1]
https://ci.inria.fr/pharo-contribution/view/Books/job/PharoBookWorkInProgress/lastSuccessfulBuild/artifact/book-result/UnifiedFFI/UnifiedFFI.pdf
