lI am trying to use libpng in program, working on Windows Mobile 6.1.
To that end i created a c++ project from template "c++ SmartDevice Class library", and added to it appropriate c source files from libpng, using visual studio project provided there as a guide, and added the directory of libpng sources to source search directory.
However, when i try to compile, i get the following errors:
error C2054: expected '(' to follow 'PNG_DLL_EXPORT' <path>\lib\lpng1512\png.h 991
In other words, first PNG_DLL_EXPORT causes an error, and after that it is an error on every following line of png.h.
What would be the cause? How that should be fixed? Is that a known issue?
Update: The exact macros used there is PNG_EXPORT. It is defined in pngconf.h as:
#define PNG_EXPORT(ordinal, type, name, args)\
PNG_EXPORTA(ordinal, type, name, args, PNG_EMPTY)
Macros used are, consequently, defined as:
/* ANSI-C (C90) does not permit a macro to be invoked with an empty argument,
* so make something non-empty to satisfy the requirement:
*/
#define PNG_EMPTY /*empty list*/
and
/* The ordinal value is only relevant when preprocessing png.h for symbol
* table entries, so we discard it here. See the .dfn files in the
* scripts directory.
*/
#ifndef PNG_EXPORTA
# define PNG_EXPORTA(ordinal, type, name, args, attributes)\
PNG_FUNCTION(PNG_EXPORT_TYPE(type),(PNGAPI name),PNGARG(args), \
extern attributes)
#endif
Down the rabbbit hole, there are:
/* In 1.5.2 the definition of PNG_FUNCTION has been changed to always treat
* 'attributes' as a storage class - the attributes go at the start of the
* function definition, and attributes are always appended regardless of the
* compiler. This considerably simplifies these macros but may cause problems
* if any compilers both need function attributes and fail to handle them as
* a storage class (this is unlikely.)
*/
#ifndef PNG_FUNCTION
# define PNG_FUNCTION(type, name, args, attributes) attributes type name args
#endif
#ifndef PNG_EXPORT_TYPE
# define PNG_EXPORT_TYPE(type) PNG_IMPEXP type
#endif
And further down:
# if (defined(_MSC_VER) && _MSC_VER < 800) ||\
(defined(__BORLANDC__) && __BORLANDC__ < 0x500)
/* older Borland and MSC
* compilers used '__export' and required this to be after
* the type.
*/
# ifndef PNG_EXPORT_TYPE
# define PNG_EXPORT_TYPE(type) type PNG_IMPEXP
# endif
# define PNG_DLL_EXPORT __export
# else /* newer compiler */
# define PNG_DLL_EXPORT __declspec(dllexport)
# ifndef PNG_DLL_IMPORT
# define PNG_DLL_IMPORT __declspec(dllimport)
# endif
# endif /* compiler */
In other file, pngpriv.h, PNG_DLL_EXPORT finally IS used:
/* See pngconf.h for more details: the builder of the library may set this on
* the command line to the right thing for the specific compilation system or it
* may be automagically set above (at present we know of no system where it does
* need to be set on the command line.)
*
* PNG_IMPEXP must be set here when building the library to prevent pngconf.h
* setting it to the "import" setting for a DLL build.
*/
#ifndef PNG_IMPEXP
# ifdef PNG_BUILD_DLL
# define PNG_IMPEXP PNG_DLL_EXPORT
# else
/* Not building a DLL, or the DLL doesn't require specific export
* definitions.
*/
# define PNG_IMPEXP
# endif
#endif
Update2: This issue is specific to compilation into dll. Compilation into lib doesn't cause the same compiler errors.
