Use gdb to find where program stuck

cdebugginggdb

My program is not working correctly.
It looks like it is stuck in an infinite loop or a bad mutex lock/unlock. But, I have no idea where the bug is.
I tried using gdb for debugging.

I can't use gdb backtrace command because I don't designate breakpoint.
And I can't designate it because I don't have any idea where the error is.

Does gdb have instrument for backtrace "on the fly"?

Best Answer

I can't use gdb backtrace command because I don't designate breakpoint.

Yes, you can.

All you need is for the inferior (being debugged) program to be stopped somewhere.

When you first attach to the program, GDB will stop all threads, and you can examine where they are. Later, you can hit Ctrl-C, and again look at all threads. A useful command is thread apply all where.

Related Solutions

C++ – How to print the full value of a long string in gdb

set print elements 0

From the GDB manual:

set print elements number-of-elements

Set a limit on how many elements of an array GDB will print. If GDB is printing a large array, it stops printing after it has printed the number of elements set by the set print elements command. This limit also applies to the display of strings. When GDB starts, this limit is set to 200. Setting number-of-elements to zero means that the printing is unlimited.

Sqlite – Improve INSERT-per-second performance of SQLite

Several tips:

Put inserts/updates in a transaction.
For older versions of SQLite - Consider a less paranoid journal mode (pragma journal_mode). There is NORMAL, and then there is OFF, which can significantly increase insert speed if you're not too worried about the database possibly getting corrupted if the OS crashes. If your application crashes the data should be fine. Note that in newer versions, the OFF/MEMORY settings are not safe for application level crashes.
Playing with page sizes makes a difference as well (PRAGMA page_size). Having larger page sizes can make reads and writes go a bit faster as larger pages are held in memory. Note that more memory will be used for your database.
If you have indices, consider calling CREATE INDEX after doing all your inserts. This is significantly faster than creating the index and then doing your inserts.
You have to be quite careful if you have concurrent access to SQLite, as the whole database is locked when writes are done, and although multiple readers are possible, writes will be locked out. This has been improved somewhat with the addition of a WAL in newer SQLite versions.
Take advantage of saving space...smaller databases go faster. For instance, if you have key value pairs, try making the key an INTEGER PRIMARY KEY if possible, which will replace the implied unique row number column in the table.
If you are using multiple threads, you can try using the shared page cache, which will allow loaded pages to be shared between threads, which can avoid expensive I/O calls.
Don't use !feof(file)!

I've also asked similar questions here and here.

Best Answer

Related Solutions

C++ – How to print the full value of a long string in gdb

Sqlite – Improve INSERT-per-second performance of SQLite

Related Topic