How to get a release build with debugging information when using cargo?

Question

The following command

$ cargo build

produces a non-optimized build with debugging information. On the contrary,

$ cargo build --release

produces an optimized build without debugging information.

Is there a way of producing an optimized build with debugging information? I need this to get meaningful profiling information.

Answer 1

If you want to use an existing profile (such as release) that normally doesn't include debug information, but add debug information just for a single build, you can use the CARGO_PROFILE_<profile_name>_DEBUG environment variable. Example:

CARGO_PROFILE_RELEASE_DEBUG=true cargo build --release

Answer 2

As of Rust 1.57, Cargo now allows for custom profiles. This allows you to define your own profile that adds debug information:

[profile.release-with-debug]
inherits = "release"
debug = true

You can then use that profile when building:

% cargo build --profile=release-with-debug
   Compiling buggin v0.1.0 (/tmp/buggin)
    Finished release-with-debug [optimized + debuginfo] target(s) in 0.48s

Prior to this version, or if you always wanted to have debugging information, you can modify the release profile to include debugging symbols:

[profile.release]
debug = true

Note that the release profile and the bench profile differ.

See also

• Can tests be built in release mode using Cargo?
• How to compile and run an optimized Rust program with overflow checking enabled
• Does Cargo support custom profiles?

Or basically any of the top search results for "rust profiling":

• Rust Profiling with Instruments and FlameGraph on OSX: CPU/Time
• Profiling Rust applications on Linux
• Profiling rust code with callgrind

Answer 3

Another option that I found that does not require changing Cargo.toml is to use the RUSTFLAGS environment variable:

$ RUSTFLAGS=-g cargo build --release