Crate crabgrind

Expand description

Valgrind Client Request interface for Rust

crabgrind wraps various Valgrind client request macros in a C functions, compiles and links against the resulting binary and exposes unsafe interface, allowing Rust programs running under Valgrind to interact with the tools and environment.

Valgrind 3.19 API coverage

Supported tool-specific client request interface:
- valgrind
- callgrind
- memcheck
- helgrind
- massif
Monitor commands interface

Quickstart

crabgrind imports macros from Valgrind’s header files, therefor you must have Valgrind installed to build the project.

Add the following to your Cargo.toml file:

[dependencies]
crabgrind = "0.1"

Examples

Print some message to the Valgrind log

use crabgrind as cg;

if matches!(cg::run_mode(), cg::RunMode::Native) {
    println!("run me under Valgrind");
} else {
    let msg = std::ffi::CString::new("Hey Valgrind!\n")?;
    cg::print(msg);
}

Exclude expensive (de)initialization code from the measurements

One way to do this would be to turn off stats collection at stratup with the --collect-atstart=no callgrind command-line attribute, and enable/disable it from the code with callgrind::toggle_collect

use crabgrind as cg;

// ... some expensive initialization

cg::callgrind::toggle_collect();
// code of interest
cg::callgrind::toggle_collect();

// ... some deinitialization

Run a closure on the real CPU while running under Valgrind

We can run on the real CPU instead of the virtual one using valgrind::non_simd_call, refer to valgrind.h for details on limitations and various ways to crash.

use crabgrind as cg;

let mut state = 0;
cg::valgrind::non_simd_call(|tid| {
    // uncomment following line to see "the 'impossible' happened"
    // println!("tid: {tid}");
    state = tid;
});

println!("tid: {state}");

Save current memory usage snapshot to a file

We’ll use Massif tool and the monitor command interface to run the corresponding Massif command.

use crabgrind as cg;
use std::ffi::CString;

let heap = String::from("alloca");

cg::monitor_command(CString::new("snapshot mem.snapshot")?);

Overhead

from Valgrind docs

The code added to your binary has negligible performance impact: on x86, amd64, ppc32, ppc64 and ARM, the overhead is 6 simple integer instructions and is probably undetectable except in tight loops.

… the code does nothing when not run on Valgrind, so you are not forced to run your program under Valgrind just because you use the macros in this file.

however, wrapping each macros in a function implies function call overhead regardless of the run mode, plus, some of the wrappers returns std::result::Result which involves branching. If you wish to compile out all (crab)Valgrind from the binary, you can wrap crabgrind calls with the feature-gate.