我正在用 python 构建一个小型的“概念验证”库系统,并希望由 c 扩展处理数据库(为了安全并阻止有人干预代码)
我编译了所有内容,现在有了我的 _databaseHandler.so 文件,但遗憾的是 python 在导入时崩溃了
我的 C 代码
#include "library.h"
#include <stdio.h>
#include <stdlib.h>
#include <mysql/mysql.h>
MYSQL connect(){
MYSQL *con = mysql_init(NULL);
const char *address = "rarehost.net";
const char *username = "MySQL-name";
const char *password = "MySQL-password";
const char *databaseName = "dbname";
const unsigned int port = 3306;
if(con == NULL){
fprintf(stderr, "%s\n", mysql_error(con));
exit(1);
}
if(mysql_real_connect(con, address, username, password, databaseName, port, NULL, 0) == NULL) {
fprintf(stderr, "%s\n", mysql_error(con));
} else{
return *con;
}
}
void finish_with_error(MYSQL *con)
{
fprintf(stderr, "%s\n", mysql_error(con));
mysql_close(con);
exit(1);
}
char* getCustomers() {
MYSQL con = connect();
if (mysql_query(&con, "SELECT * FROM cars")) {
finish_with_error(&con);
}
MYSQL_RES *result = mysql_store_result(&con);
int num_fields = mysql_num_fields(result);
MYSQL_ROW row;
while((row = mysql_fetch_row(result))) {
for (int i = 0; i < num_fields; ++i) {
printf("%s ", row[i] ? row[i] : "NULL");
/*return row[i] ? row[i] : "NULL";*/
}
printf("\n");
}
return "hi";
}
是的,我知道它只是返回 hi,这是出于测试目的,直到我设法将其导入 python 中。
我的头文件
#ifndef DATABASEHANDLER_LIBRARY_H
#define DATABASEHANDLER_LIBRARY_H
#include <mysql/mysql.h>
#include <stdio.h>
#include <stdlib.h>
char* getCustomers();
#endif //DATABASEHANDLER_LIBRARY_H
我的界面文件
%module databaseHandler
%{
#include "library.h"
#include <mysql/mysql.h>
%}
char* getCustomers();
最后但并非最不重要的一点是我的 makefile
_databaseHandler.so: library.o library_wrap.o
gcc -shared library.o library_wrap.o -o _databaseHandler.so
library.o:
gcc -c -fPIC library.c -I/usr/include/mariadb/mysql
library_wrap.o:
swig -python library.i
gcc -c -fPIC library_wrap.c -I/usr/include/python3.7
这是让我做噩梦的输出:
Traceback (most recent call last):
File "/home/user/CLionProjects/databaseHandler/databaseHandler.py", line 14, in swig_import_helper
return importlib.import_module(mname)
File "/usr/lib/python3.7/importlib/__init__.py", line 127, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "<frozen importlib._bootstrap>", line 1006, in _gcd_import
File "<frozen importlib._bootstrap>", line 983, in _find_and_load
File "<frozen importlib._bootstrap>", line 967, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 670, in _load_unlocked
File "<frozen importlib._bootstrap>", line 583, in module_from_spec
File "<frozen importlib._bootstrap_external>", line 1043, in create_module
File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
ImportError: /home/user/CLionProjects/databaseHandler/_databaseHandler.so: undefined symbol: mysql_query
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "test.py", line 1, in <module>
import databaseHandler
File "/home/user/CLionProjects/databaseHandler/databaseHandler.py", line 17, in <module>
_databaseHandler = swig_import_helper()
File "/home/user/CLionProjects/databaseHandler/databaseHandler.py", line 16, in swig_import_helper
return importlib.import_module('_databaseHandler')
File "/usr/lib/python3.7/importlib/__init__.py", line 127, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
ImportError: /home/user/CLionProjects/databaseHandler/_databaseHandler.so: undefined symbol: mysql_query
(python程序只是导入和一个 print("hello") 函数)
这可能是一些愚蠢的小错误,但我一生都找不到它。如有任何帮助,我们将不胜感激。
最佳答案
由于您的库使用 mysql 中的函数,因此您需要在链接时将该库链接到适当的库。 (还有其他方法可以安排在运行时定义符号,但这是迄今为止最明智的选择)
因此,您需要在 Makefile 中添加如下内容:
_databaseHandler.so: library.o library_wrap.o
gcc -shared library.o library_wrap.o -o _databaseHandler.so -lmysql -L/path/to/lib
(您需要提供准确的库名称和路径,以便从您用来提供它的包中进行链接,如果不清楚的话,通常有一个 pkgconfig 文件可以帮助解决此问题或某些文档)。
关于python - python 导入时出现 SWIG 错误 'undefined symbol: mysql_query',我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/66247835/