bug when I trying install the mariadb with pip

[loki0b]

I was not able to install mariadb-connector with pip because it was getting a compiler error when building.
Probably because one of the flags -Werror=format-security which treats warning as error.

The output of error:

mariadb/mariadb_cursor.c: In function ‘MrdbCursor_execute_text’:
  mariadb/mariadb_cursor.c:1138:39: error: passing argument 2 of ‘PyBytes_AsStringAndSize’ from incompatible pointer type [-Wincompatible-pointer-types]
   1138 |         PyBytes_AsStringAndSize(stmt, &statement, (Py_ssize_t *)&statement_len);
        |                                       ^~~~~~~~~~
        |                                       |
        |                                       const char **
  In file included from /usr/include/python3.12/Python.h:50,
                   from ./include/mariadb_python.h:21,
                   from mariadb/mariadb_cursor.c:20:
  /usr/include/python3.12/bytesobject.h:56:12: note: expected ‘char **’ but argument is of type ‘const char **’
     56 |     char **s,           /* pointer to buffer variable */
        |     ~~~~~~~^
  error: command '/usr/bin/gcc' failed with exit code 1

Since the function PyBytes_AsStringAndSize from bytesobjects.h expectate a char** and not a const char** I remove the "pass by reference" and add a explicit conversion of type of statement to (char**).

After that I could install the mariadb package with pip using the source code that I edit.

[vkabadzhova]

Hey, there! Same issue here. Do you need to recompile the c files somehow after the change? Please, specify the exact steps you went through:) Thanks in advance.

[loki0b]

Yes. It needs to you install the package from source.
After make this changes above just go to the package root then run pip install .

[9EOR9]

Why did you remove the address (&) ?

[loki0b]

Hello. I remove it to convert directly to char**.
I tried changing the statement type from const char* to char* and it also worked.
However, I don't know what is the best way to do it and whether the latter could cause problems.

[jcmdln]

Instead of casting away the const incorrectly, within this function you can instead drop const from the declaration of statement:

diff --git a/mariadb/mariadb_cursor.c b/mariadb/mariadb_cursor.c
index 65fab74..191f93a 100644
--- a/mariadb/mariadb_cursor.c
+++ b/mariadb/mariadb_cursor.c
@@ -1125,7 +1125,7 @@ MrdbCursor_execute_text(MrdbCursor *self, PyObject *stmt)
 {
     int rc;
     MYSQL *db;
-    const char *statement;
+    char *statement;
     size_t statement_len= 0;
 
     MARIADB_CHECK_CONNECTION(self->connection, NULL);

[loki0b]

Hey. I made these changes and updated the pr. Thanks :)

[tkuschel]

When you remove const from statement, you will break the line with PyUnicode_AsUTF8AndSize():

statement = PyUnicode_AsUTF8AndSize(stmt, (Py_ssize_t *)&statement_len);

That funciton is defined as

const char *PyUnicode_AsUTF8AndSize(PyObject *unicode, Py_ssize_t *size)

seen in https://docs.python.org/3/c-api/unicode.html.
This returns a const char *. And this throws a warning in the upper removing of const from statement.

Also the function `mysql_send_query(db, statement, (long)statement_len) is defined as

int mysql_send_query(MYSQL * mysql,
                     const char * query,
                     unsigned long length);

So either we cast the &statement to a line like

        PyBytes_AsStringAndSize(stmt, (char **)&statement, (Py_ssize_t *)&statement_len);

or for more readability:

    } else if (Py_TYPE(stmt) == &PyBytes_Type)
    {
        char *sbuf;
        PyBytes_AsStringAndSize(stmt, &sbuf, (Py_ssize_t *)&statement_len);
        statement = sbuf;
    }

[tkuschel]

Within this function, we can also exchange the size_t with Py_ssize_t, then we have less castings.

static PyObject *
MrdbCursor_execute_text(MrdbCursor *self, PyObject *stmt)
{
    int rc;
    MYSQL *db;
    const char *statement;
    Py_ssize_t statement_len= 0;

    MARIADB_CHECK_CONNECTION(self->connection, NULL);

    if (Py_TYPE(stmt) == &PyUnicode_Type)
    {
        statement = PyUnicode_AsUTF8AndSize(stmt, &statement_len);
    } else if (Py_TYPE(stmt) == &PyBytes_Type)
    {
        PyBytes_AsStringAndSize(stmt, (char **)&statement, &statement_len);
    }
    else {
        PyErr_SetString(PyExc_TypeError, "Parameter must be a string or bytes");
        return NULL;
    }
    db= self->connection->mysql;

    MARIADB_BEGIN_ALLOW_THREADS(self->connection);
    rc= mysql_send_query(db, statement, (long)statement_len);
    MARIADB_END_ALLOW_THREADS(self->connection);

    if (rc)
    {
        mariadb_throw_exception(db, NULL, 0, NULL);
        return NULL;
    }
    Py_RETURN_NONE;
}