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//
// GTMMethodCheck.h
//
// Copyright 2006-2008 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy
// of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
//
#import <Foundation/Foundation.h>
#import <stdio.h>
#import <sysexits.h>
/// A macro for enforcing debug time checks to make sure all required methods are linked in
//
// When using categories, it can be very easy to forget to include the
// implementation of a category.
// Let's say you had a class foo that depended on method bar of class baz, and
// method bar was implemented as a member of a category.
// You could add the following code:
// @implementation foo
// GTM_METHOD_CHECK(baz, bar)
// @end
// and the code would check to make sure baz was implemented just before main
// was called. This works for both dynamic libraries, and executables.
//
// Classes (or one of their superclasses) being checked must conform to the
// NSObject protocol. We will check this, and spit out a warning if a class does
// not conform to NSObject.
//
// This is not compiled into release builds.
#ifdef DEBUG
#ifdef __cplusplus
extern "C" {
#endif
// If you get an error for GTMMethodCheckMethodChecker not being defined,
// you need to link in GTMMethodCheck.m. We keep it hidden so that we can have
// it living in several separate images without conflict.
// Functions with the ((constructor)) attribute are called after all +loads
// have been called. See "Initializing Objective-C Classes" in
// http://developer.apple.com/documentation/DeveloperTools/Conceptual/DynamicLibraries/Articles/DynamicLibraryDesignGuidelines.html#//apple_ref/doc/uid/TP40002013-DontLinkElementID_20
__attribute__ ((constructor, visibility("hidden"))) void GTMMethodCheckMethodChecker(void);
#ifdef __cplusplus
};
#endif
// This is the "magic".
// A) we need a multi layer define here so that the stupid preprocessor
// expands __LINE__ out the way we want it. We need LINE so that each of
// out GTM_METHOD_CHECKs generates a unique class method for the class.
#define GTM_METHOD_CHECK(class, method) GTM_METHOD_CHECK_INNER(class, method, __LINE__)
#define GTM_METHOD_CHECK_INNER(class, method, line) GTM_METHOD_CHECK_INNER_INNER(class, method, line)
// B) Create up a class method called xxGMethodCheckMethod+class+line that the
// GTMMethodCheckMethodChecker function can look for and call. We
// look for GTMMethodCheckMethodChecker to enforce linkage of
// GTMMethodCheck.m.
#define GTM_METHOD_CHECK_INNER_INNER(class, method, line) \
+ (void)xxGMMethodCheckMethod ## class ## line { \
void (*addr)() = GTMMethodCheckMethodChecker; \
if (addr && ![class instancesRespondToSelector:@selector(method)] \
&& ![class respondsToSelector:@selector(method)]) { \
fprintf(stderr, "%s:%d: error: We need method '%s' to be linked in for class '%s'\n", \
__FILE__, line, #method, #class); \
exit(EX_SOFTWARE); \
} \
}
#else // !DEBUG
// Do nothing in release.
#define GTM_METHOD_CHECK(class, method)
#endif // DEBUG
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