// 当main函数试图调用foo函数时,foo函数地址为0,发生非法地址访问错误__attribute__((weakref)) voidfoo(); intmain() {foo(); }// 改进方法__attribute__((weakref)) voidfoo(); intmain() {if(foo)foo(); } 库中定义的弱符号可以被用户定义的强符号所覆盖,从而使得程序可以使用自定义版本的库函数...
在GCC的官方文档中,对weak和weakref的描述如下: http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function-Attributes weak The weak attribute causes the declaration to be emitted as a weak symbol rather than a global. This is primarily useful in defining library functions which can be ove...
The weakref attribute marks a declaration as a weak reference. Without arguments, it should be accompanied by an alias attribute naming the target symbol. Optionally, the target may be given as an argument to weakref itself. In either case, weakref implicitly marks the declaration as weak. Witho...
一般对于未定义的弱引用,链接器默认其为0,或者是一个特殊的值,以便于程序代码能够识别。 在GCC中,我们可以通过使用__attribute__((weakref))扩展关键字来声明对一个外部函数的引用为弱引用。比如下面这段代码: __attribute__ ((weakref)) void foo(); int main() { foo();...
(x),0)) #define _public_ __attribute__ ((visibility("default"))) #define _hidden_ __attribute__ ((visibility("hidden"))) #define _weakref_(x) __attribute__((weakref(#x))) #define _alignas_(x) __attribute__((aligned(__alignof(x))) #define _cleanup_(x) __attribute__((cle...
1__attribute__((weakref))voidfoo(); 2intmain() 3{ 4foo(); 5} 6 我们可以将它编译成一个可执行文件，GCC并不会报链接错误。但是当我们运行这个可执行文件时，会发生运行错误。因为当main函数试图调用foo函数时，foo函数的地址为0，于是发生了非法地址访问的错误。一个改进的例子是： 1__attribute__...
对于函数,需要使用__attribute__((weak))定义弱符号,否则默认为强符号.而__attribute__((weakref("替代函数名"))). 强符号不可重复定义否则链接器报错 在强弱符号同时存在时,编译器会首选强符号. 有且只有多个弱符号时选择占用空间最大的一个 而弱连接在指定的替代函数未被实现时是未定义的(if(函数名)判定...
The __has_attribute() built-in can be used with both gcc and Oracle Developer Studio compilers to test for recognized attributes.The following attributes are new in Oracle Developer Studio 12.6 C++: aligned, deprecated, weak(alias), weakref, packed, tls_model, vector_size, and visibility....
TARGET_FUNCTION_ATTRIBUTE_INLINABLE_P: Target AttributesTARGET_FUNCTION_OK_FOR_SIBCALL: Tail CallsTARGET_FUNCTION_VALUE: Scalar ReturnTARGET_GIMPLIFY_VA_ARG_EXPR: Register ArgumentsTARGET_HANDLE_OPTION: Run-time TargetTARGET_HAVE_CTORS_DTORS: Macros for Initialization...
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