Debugging-related flags¶
Below are some flags for cairo-run that you may use to debug errors in your program. In addition
to these flags, you can always add a hint with a print statement to output the value
of a certain identifier or a memory cell.
--print_info¶
Instructs cairo-run to print the info section, which contains the following information:
The number of executed steps.
The number of used memory cells.
The values of the registers at the end of the execution.
The segment relocation table.
Note that you may see values of the form x:y in the output (e.g., 4:2).
Those are relocatable values, see Segments for more information.
--print_memory¶
Prints the addresses and values of the memory cells that were assigned during execution.
If you get an error that refers to a specific memory cell, it may be helpful to examine the value of that cell and the adjacent memory cells.
--steps¶
You can control the number of steps that cairo-run performs using the
--steps flags. This is an optional parameter – if you don’t specify it,
cairo-run will run until the program ends (after the ret instruction called by main()).
--no_end¶
If you specify an exact number of steps, and the program does not end within that number of
steps, cairo-run will throw an error (End of program was not reached).
You can instruct cairo-run to ignore this using the --no_end flag.
Specifying the number of steps, combined with the --no_end flag can be used to debug a
program, as it allows you to examine the values of the memory and registers after the program has
run the specified amount of steps.
--debug_error¶
When an error occurs, the memory and the info sections are not printed by default.
You may use the --debug_error to print them anyway.
The idea is that by examining the values of the memory and the info sections, you may be able
to better understand the source of the error.
--profile_output profile.pb.gz¶
Outputs a profile result file that can be viewed with pprof.
If you have go installed you can view the result using:
go tool pprof --web profile.pb.gz
Alternatively, you can use the golang docker image (you’ll need to install docker first):
docker run --net=host -v$PWD:/tmp starkwarelibs/pprof profile.pb.gz
Or build the docker image manually using this docker file:
FROM golang
RUN apt update
RUN apt install -y graphviz
WORKDIR /tmp
ENTRYPOINT ["go", "tool", "pprof", "--http", "localhost:8080", "--no_browser"]