gdb: "No symbol table is loaded"

Question

I keep getting this error mesage when trying to add a breakpoint in gdb.

I've used these commands to compile:

gcc -g main.c utmpib2.c -o main.o
and:
cc -g main.c utmpib2.c -o main.o
and also:
g++ -g main.c utmpib2.c -o main.o

I also tried "-ggdb" instead of "-g" and I still get that error message.

I then execute gdb:

$gdb

In gdb:

(gdb)exec-file main.o
(gdb)break 59
No symbol table is loaded. Use the "file" command.

Answer 1

You have to add extra parameter -g, which generates source level debug information. It will look like:

gcc -g prog.c

After that you can use gdb in common way.

Answer 2

First of all, what you have is a fully compiled program, not an object file, so drop the .o extension. Now, pay attention to what the error message says, it tells you exactly how to fix your problem: "No symbol table is loaded. Use the "file" command."

(gdb) exec-file test
(gdb) b 2
No symbol table is loaded.  Use the "file" command.
(gdb) file test
Reading symbols from /home/user/test/test...done.
(gdb) b 2
Breakpoint 1 at 0x80483ea: file test.c, line 2.
(gdb) 

Or just pass the program on the command line.

$ gdb test
GNU gdb (GDB) 7.4
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
[...]
Reading symbols from /home/user/test/test...done.
(gdb) b 2
Breakpoint 1 at 0x80483ea: file test.c, line 2.
(gdb) 

Answer 3

I have the same problem and I followed this Post, it solved my problem.

Follow the following 2 steps:

1. Make sure the optimization level is -O0
2. Add -ggdb flag when compiling your program

Good luck!

Answer 4

Whenever gcc on the compilation machine and gdb on the testing machine have differing versions, you may be facing debuginfo format incompatibility.

To fix that, try downgrading the debuginfo format:

gcc -gdwarf-3 ...
gcc -gdwarf-2 ...
gcc -gstabs ...
gcc -gstabs+ ...
gcc -gcoff ...
gcc -gxcoff ...
gcc -gxcoff+ ...

Or match gdb to the gcc you're using.

Answer 5

I met this issue this morning because I used the same executable in DIFFERENT OSes: after compiling my program with gcc -ggdb -Wall test.c -o test in my Mac(10.15.2), I ran gdb with the executable in Ubuntu(16.04) in my VirtualBox.

Fix: recompile with the same command under Ubuntu, then you should be good.

Answer 6

No clue why this worked, but loading the symbol file separately did the trick for me:

(gdb) symbol-file "myapp.exe"
(gdb) target exec myapp.exe
(gdb) run