Casting label type in gdb

Question

I am trying to learn assembly and I am using Ubuntu, I want to see the value of a label using GDB. Issue is that the label is one byte big and I cant cast it as just "p (byte)'label_name' ". And GDB does not seem to work if i dont tell it what the label size is.

Answer 1

p (char)label_name works for me. GDB commands use C type names. (Showing it as a number and the ASCII character it represents for char. C doesn't have a separate type for 8-bit integer).

C doesn't have a type called byte, so (byte)foo is an error.

As Jester says, x /b &label_name might be what you want to eXamine memory, especially if you want to see multiple bytes starting from a certain point.

Within GDB, help x and help p will show details on how to use it.

Related:

• GDB shows error message when trying to print a variable in an Assembly program
• Address of an ASM label in GDB - how GDB gets symbol type info for debugging C programs. Older GDB used to default to int or something, now it prints 'x' has unknown type; cast it to its declared type like you were getting.
• How to print <incomplete type> variable in gdb