lldb_folly_formatter

LLDB Data formatters for folly

Set up

You need g++, cmake, ninja and a prebuilt version of folly. For example, on Fedora you should be able to do this by executing

sudo dnf groupinstall "Development Tools" -y
sudo dnf install clang folly-static cmake ninja-build

Finally, you need lldb, which you can install from an existing package or build it yourself.

sudo dnf install lldb

How to build

./build.sh

The produced artifacts will be in the ./out/bin folder. This folder can't be changed as the test framework requires it to be fixed.

How to run the tests

./run_tests.sh

How to use a formatter

For example, let's pick the fbstring formatter.

cd <repo_root>
lldb ./build/src/fbstring/fbstring_test 

Now we are inside lldb's cli. Let's run the program until line 7, where the variable fbstr is defined.

(lldb) b 7     # this sets a breakpoint at line 7
(lldb) r       # this run the program

Now let's print the variable

(lldb) p fbstr

Which gives us as output

(folly::fbstring) $0 = {
  store_ = {
     = {
      bytes_ = "aaaaaaaaaa"
      small_ = "aaaaaaaaaa"
      ml_ = (data_ = "", size_ = 24929, capacity_ = 936889459981410112)
    }
  }
}

Lots of gibberish, right?

Now let's add the formatter and reprint the variable

(lldb) command script import ./src/fbstring/fbstring_formatter.py
(lldb) p fbstr

Which prints

(folly::fbstring) $0 = (folly::fbstring) "aaaaaaaaaa"

Nice, right? This is exactly what the user expects to see.