I'm having some trouble moving a C application from
a test machine to production. The program, which uses
the small wrapper around mysql_query() shown below, runs
flawlessly on the test machine (hours of runtime; tens
of thousands if not a million+ queries).
On the production machine, the program will execute exactly
10 queries, then segfault. The 10 queries which are executed
before the fault are a mix of INSERT, DELETE, and SELECTs
which return both empty and non-empty sets. The last query
is a SELECT which returns (well -- is *supposed* to return)
an empty set.
The problem is twofold: The call to mysql_field_count()
returns 1 (should be 0) and upon reaching the
mysql_store_result() function call, the program segfaults.
I have tried switching around the two statements (as per the
examples in the docs), to no avail.
Both machines run RH Linux 7.1, and use GCC 2.96-85
Test machine:
- MySQL 3.23.39-1 RPM from mysql.com
- glibc-2.2-12
- kernel v. 2.2 (as included in RH 7.1)
Production machine:
- MySQL 3.23.43-1 RPM from mysql.com
- glibc-2.2.4-19
- updated kernel (2.4)
I've been trying all kinds of up- and downgrades of gcc
and the MySQL packages, different levels of compiler
optimizations, etc., but can't seem to get around this
problem. If anyone has any hint as to what is wrong, I
would appreciate hearing from you.
[code snippet below]
/ Carsten
MYSQL_RES *mysql_query_e(char *query, char* message, int lineno) {
int result;
char *errmsg;
MYSQL_RES *resultset;
// Do the query
if (mysql_query(mysql, query)) {
printf("----------------------------------------\n"
"ERROR: Error when querying database on line %d.\n"
"--\n%s\n\nQuery:\n %s\n\nError message:\n%d: %s\n",
lineno, message, query, mysql_errno(mysql),
mysql_error(mysql));
fflush(stdout);
exit(2);
}
// Check whether we should expect any data
if (mysql_field_count(mysql)) {
// On the 11th query...
// ... this line prints "1" where it should say "0":
printf ("%d fields in result\n", mysql_field_count(mysql));
// ... and the following line segfaults:
resultset = mysql_store_result(mysql);
if (NULL == resultset) {
printf("Error: Could not get result for query on line %d\n"
"--\nExpected %d columns\n"
"%s\n\nQuery:\n %s\n\nError message:\n%d:\n%s\n",
lineno, mysql_field_count(mysql),
message, query, mysql_errno(mysql),
mysql_error(mysql));
fflush(stdout);
exit(2);
}
// yes, there is data. Return the the result to caller
return resultset;
}
// No data, no columns. That's fine
return NULL;
}
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