crunch

Memory profiling tool for macOS, inspired by valgrind's memcheck.

Installation

You will need:

• Python 3
• docopt (pip3 install docopt)
• jinja2 (pip3 install jinja2)
• GNU make
• gcc

git clone https://github.com/AjayMT/crunch.git
cd crunch
pip3 install docopt jinja2
python3 install.py

The install script (install.py) will guide you through the installation process.

Usage and mechanism

crunch [options] <program> [<arguments>...]

(Running crunch --help will print a help message with a description of all the options.)

crunch will execute program with the specified arguments. program runs as normal, except:

• malloc and free are 'overridden' during runtime (see DYLD_INTERPOSE) and wrapped with extra instrumentation
  • allocations are tracked as pointer+size pairs in a hash table. Making malloc and free slower and/or more expensive is pretty much unavoidable, but a better hash table implementation will likely improve performance significantly (see src/crunch_set.c)
  • as of now crunch also synchronizes calls to malloc and free, which severely impacts concurrent programs. There is probably a better way to approach multi-threading than wrapping malloc and free in a mutex
• signal handlers are attached to the following signals:
  • SIGSEGV and SIGABRT: crunch will report an abnormal (fatal) exit and record the offending memory address (i.e the pointer that caused the segfault/abort)

Upon exit, crunch will create a crunch_out directory and store its results there.

crunch_out
├── fatal # this file only exists if the program exits abnormally
├── heap # this folder stores the contents of the heap upon exit, each file is an address
│   └── 0x7fa45ec02af0
├── report.html
└── stats

Each file in the heap directory stores the contents of a single allocation remaining on the heap. report.html reports all of the information recorded by crunch.

Example usage:

// /tmp/program.c
#include <stdlib.h>

int main(int argc, char *argv[])
{
  char *buf = malloc(10);
  buf[0xffffff] = 'a';
  free(buf);
  return 0;
}

$ cc program.c
$ crunch a.out

crunch: SIGSEGV illegal access: address 0x7f828b402aef

writing crash info...
crash info written to /tmp/crunch_out/fatal

=== crunch ===
1 remaining heap allocations
  0x7f828a402af0 : 10 bytes

dumping heap...
heap contents written to /tmp/crunch_out/heap
crunch report written to /tmp/crunch_out/report.html

Roadmap

planned features

• virtualize resources for better instrumentation?
• track memory usage over time
• view heap snapshots at any point of time during execution

misc

• create a Homebrew formula
• measure performance

Built With

• c
• html
• python