问对error()的Python C API调用绑定到libc实现，而不是本地实现

EN

#include <stdio.h>
#include <Python.h>

static PyObject* call_error(PyObject *self, PyObject *args);
static PyMethodDef module_methods[] = {
     {"error", call_error, METH_NOARGS, "call error"},
     {NULL, NULL, 0, NULL}
};

static struct PyModuleDef module_defs = {
     PyModuleDef_HEAD_INIT,
     "Test", "Test", -1, module_methods, NULL, NULL, NULL, NULL};

PyObject* PyInit_Test(void)
{
     PyObject *module = PyModule_Create(&module_defs);
     return module;
}

void error(const char* fmt, ...);

PyObject* call_error(PyObject *self, PyObject *args)
{
     error("Error!");
     Py_RETURN_NONE;
}

void error(const char* fmt, ...)
{
     va_list ap;
     va_start(ap, fmt);
     vprintf(fmt, ap);
     va_end(ap);
}

GNU gdb (Ubuntu 8.1-0ubuntu3) 8.1.0.20180409-git
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Reading symbols from python3...(no debugging symbols found)...done.
(gdb) r -c 'import Test; Test.error()'
Starting program: /usr/bin/python3 -c 'import Test; Test.error()'
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
/usr/bin/python3:
Program received signal SIGSEGV, Segmentation fault.
__strchrnul_sse2 () at ../sysdeps/x86_64/multiarch/../strchr.S:32
32  ../sysdeps/x86_64/multiarch/../strchr.S: No such file or directory.
(gdb) where
#0  __strchrnul_sse2 () at ../sysdeps/x86_64/multiarch/../strchr.S:32
#1  0x00007ffff6c2c432 in __find_specmb (format=0x4 <error: Cannot access memory at
#     address 0x4>) at printf-parse.h:108
#2  _IO_vfprintf_internal (s=0x7fffffffae60, format=0x4 <error: Cannot access memory at 
#     address 0x4>, ap=0x7fffffffd5b0) at vfprintf.c:1320
#3  0x00007ffff6c2f680 in buffered_vfprintf (s=s@entry=0x7ffff6fbd680 <_IO_2_1_stderr_>,
#     format=format@entry=0x4 <error: Cannot access memory at address 0x4>,
#     args=args@entry=0x7fffffffd5b0) at vfprintf.c:2329
#4  0x00007ffff6c2c726 in _IO_vfprintf_internal (s=0x7ffff6fbd680 <_IO_2_1_stderr_>,
#     format=format@entry=0x4 <error: Cannot access memory at address 0x4>, 
#     ap=ap@entry=0x7fffffffd5b0) at vfprintf.c:1301
#5  0x00007ffff6cef9bb in error_tail (status=status@entry=-161613509, 
#     errnum=errnum@entry=0, message=message@entry=0x4 <error: Cannot access memory at 
#     address 0x4>, args=args@entry=0x7fffffffd5b0) at error.c:271
#6  0x00007ffff6cefb3d in __error (status=-161613509, errnum=0, message=0x4 
#     <error: Cannot access memory at address 0x4>) at error.c:321
#7  0x00007ffff65df82e in call_error (self=0x7ffff67f3548, args=0x0) at test.c:24
#8  0x00000000004c5352 in _PyCFunction_FastCallKeywords ()
#9  0x000000000054ffe4 in ?? ()
#10 0x00000000005546cf in _PyEval_EvalFrameDefault ()
#11 0x000000000054fbe1 in ?? ()
#12 0x0000000000550b93 in PyEval_EvalCode ()
#13 0x000000000042c4ca in PyRun_SimpleStringFlags ()
#14 0x0000000000441918 in Py_Main ()
#15 0x0000000000421ff4 in main ()

> ./main
Hi there

#include <stdio.h>
#include <stdlib.h>
#include <dlfcn.h>
#include <errno.h>
#include <stdarg.h>

typedef void*(*arbitrary)();

extern void error(const char* fmt, ...);

int main(int argc, char **argv)
{
     void *handle;
     arbitrary my_function;

     handle = dlopen("./libtest.so", RTLD_LAZY | RTLD_GLOBAL);
     if (!handle) {
      fprintf(stderr, "%s\n", dlerror());
      exit(EXIT_FAILURE);
     }

     dlerror();    /* Clear any existing error */

     *(void**)(&my_function) = dlsym(handle,"foo");
     (void) my_function();

     // Note: binding using dlsym(handle, "error") works too

     dlclose(handle);
     exit(EXIT_SUCCESS);
}

#include <stdio.h>
#include <stdarg.h>

extern void error(const char* fmt, ...);
extern void foo(void);

void foo(void)
{
     error("Hi there\n");
}

void error(const char* fmt, ...)
{
     va_list ap;
     va_start(ap, fmt);
     vprintf(fmt, ap);
     va_end(ap);
}