Обсуждение: PQconnectdbParams returns exit value 01 (from gdb).

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PQconnectdbParams returns exit value 01 (from gdb).

От
Andrei Petru Mura
Дата:
I'm trying to create a connection to my database with libpq. Bellow is my code:

PGconn *connect(char *file_path) {
        const char **keywords;
        const char **values;
        char *line = malloc(LINE_SIZE);
        char *prop, *val, *tmp;
        int i = 0, j = 0, k = 0;
        FILE *creds = fopen(file_path, "r");

        if (creds == NULL) {
                LOG("%s", "error: cannot open credentials file.\n");
                exit(1);
        }

        keywords = malloc(6 * sizeof(char *));
        values = malloc(6 * sizeof(char *));

        while (fgets(line, LINE_SIZE, creds) != NULL) {
                if (line[strlen(line) - 1] == '\n')
                        line[strlen(line) - 1] = '\0';
                prop = line;
                while(*(prop++) != '=') {
                        i++;
                }
                tmp = prop;
                prop = malloc(i + 1);
                strncpy(prop, line, i);
                prop[i] = '\0';
                keywords[j++] = prop;
                val = malloc(strlen(line) - strlen(prop) + 1);
                strcpy(val, tmp);
                values[k++] = val;
                i = 0;
        }

        keywords[++j] = NULL;
        values[++k] = NULL;
printf("%s %s %s %s %s\n", keywords[0], keywords[1], keywords[2], keywords[3], keywords[4]); //everything is printed well here
printf("%s %s %s %s %s\n", values[0], values[1], values[2], values[3], values[4]); //here also

        PGconn *conn = PQconnectdbParams(keywords, values, 1);

        if (PQstatus(conn) != CONNECTION_OK) {
                fprintf(stderr, "%s\n", PQerrorMessage(conn));
                exit(1);
        }

        return conn;

}

If I run that code from main(), the printf works fine and nothing else is printed after. But trying to use that connection, I realized that in fact the PQconnectdbParams function returns value 01 (after debugging with gdb).

If I try to connect my database with the credentials from specified file, it works well.

Can anybody help me on solving that issue?

Re: PQconnectdbParams returns exit value 01 (from gdb).

От
Tom Lane
Дата:
Andrei Petru Mura <mapandrei@gmail.com> writes:
> I'm trying to create a connection to my database with libpq. Bellow is my
> code:

>         keywords = malloc(6 * sizeof(char *));
>         values = malloc(6 * sizeof(char *));

That looks less than safe ... what happens if you have more than five
lines in the creds file?

>         while (fgets(line, LINE_SIZE, creds) != NULL) {
>                 if (line[strlen(line) - 1] == '\n')
>                         line[strlen(line) - 1] = '\0';
>                 prop = line;
>                 while(*(prop++) != '=') {
>                         i++;
>                 }
>                 tmp = prop;
>                 prop = malloc(i + 1);
>                 strncpy(prop, line, i);
>                 prop[i] = '\0';
>                 keywords[j++] = prop;
>                 val = malloc(strlen(line) - strlen(prop) + 1);
>                 strcpy(val, tmp);
>                 values[k++] = val;
>                 i = 0;
>         }

This has got a few issues, like it'll die badly if there's no '='
in a line, and not behave too well if a line overruns the fixed
buffer length.

>         keywords[++j] = NULL;
>         values[++k] = NULL;

But your real problem is here, where you're leaving undefined holes
in the arrays.  These should be j++ and k++, not ++j and ++k.
If malloc doesn't give you back all-zeroes storage, PQconnectdbParams
will be led to try to dereference garbage pointer values, resulting
in your SIGSEGVs.
        regards, tom lane