C:在编译时或运行时检查该变量是否具有静态存储类说明符

问题描述

是否可以在编译时或运行时以某种方式检查该变量是否具有 static 存储类说明符?

Is it possible somehow to check at compile time or at run time that variable has static storage-class specifier?

示例:

static int v1;
int        v2;

bool r1 = is_static(v1); /* true */
bool r2 = is_static(v2); /* false */

推荐答案

好吧，原来我之前的回答对静态全局变量不起作用，所以我设计了这个程序，可以检查全局变量是否被声明为静态.它的工作方式是 dysym() 在符号表中找不到静态全局变量，所以我只检查它的输出.它还使用布尔值引用变量，以确保它确实存在.

Ok, turns out that my previous answer didn't work for static global variables, so I have devised this program that can check whether a global variable is declared static. The way it works is that dysym() can't find static globals in the symbol table, so I just check it's output. It also references the variable with a boolean and, to ensure it actually exists.

#include <stdio.h>
#include <dlfcn.h>

char* a = "hello, world";
static char* b = "hello, world";

#define is_static(name) \
  (is_sym_static(#name) && &name)

_Bool is_sym_static(const char* const name)
{
  void* hdl = dlopen(NULL, 0); // TODO: optimise by only calling this once.
  return dlsym(hdl, name) == NULL;
}

int main(int argc, char** argv)
{
  printf("%i\n", is_static(a)); // prints 0
  printf("%i\n", is_static(b)); // prints 1
}

这必须用-ldl -Wl,--export-dynamic 编译，以确保所有变量都在符号表中结束.这不适用于局部变量，但我们可以将它与我之前的答案结合起来......

This must be compiled with -ldl -Wl,--export-dynamic, to ensure that all variables end up in the symbol table. This doesn't work for local variables, but we can combine it with my previous answer and...

#include <stdio.h>
#include <dlfcn.h>
#include <sys/resource.h>

static char* stack_start;

#define is_static(name) \
  (is_addr_static(&name) && is_sym_static(#name) && &name)

_Bool is_sym_static(const char* const name)
{
  void* hdl = dlopen(NULL, 0); // TODO: optimise by only calling this once.
  return dlsym(hdl, name) == NULL;
}

_Bool is_addr_static(void* var)
{
  struct rlimit stack;
  getrlimit(RLIMIT_STACK, &stack); // TODO: optimise by only calling this once.
  char* stack_end = stack_start - stack.rlim_cur;
  return !((char*)var < stack_start && (char*)var > stack_end);
}

char*        a = "hello, world";
static char* b = "hello, world";

int main(int argc, char** argv)
{
  char _;
  stack_start = &_;
  char*        c = "hello, world";
  static char* d = "hello, world";
  printf("%i\n", is_static(a)); // prints 0
  printf("%i\n", is_static(b)); // prints 1
  printf("%i\n", is_static(c)); // prints 0
  printf("%i\n", is_static(d)); // prints 1
}

现在检测全局和局部静态变量.然而，我认为没有必要这样做，因为局部静态和全局静态是根本不同的东西.

This now detects both global and local static variables. I see no reason to need this however, since local static and global static are fundamentally different things.

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