Rust Debugging Paper Cuts

Thu, Sep 20, 2018

These are some of the pain points I have felt while trying debug Rust code in GDB. Some of them may be already solved problems but I don’t know the solution yet.

Don’t step in to standard library source code

This is a major issue step accidentally into rust std source code. Then do next command for few times till get out of it. More generally it would be nice to have command that will omit stepping into a few selected crates.

While writing this post, I discovered finish which steps out the current stackframe. That is a neat workaround for now.

Enable gdb history by default for rust-gdb

I thought it’s really weird that gdb does have history of commands of the last run. After typing the same commands again and again, I simply googled and found that gdb infact has history but it’s just disabled by default.

Inspect return value of functions with expression as return value

I am usually at the end of the function defintion but I don’t know how I can print the return value of the function. According to SO, again finish comes to the rescue. When you run it, it also gives the values returned by the last stack frame. The problem with this approach is we can’t look at the locals variables and return value at the same time

The try operator dance

When the result of expression with try operator fails, then as you run next command first you jump to } at the end of function and then back to the ? mark and then again back }.