Nim + musl + pcre + libressl/openssl

This repo contains a generic ~config.nims~ that adds a Nim “sub-command” or task named musl. You can simply add that file to your Nim project, and run nim musl foo.nim with optional -d:pcre and/or -d:libressl / -d:openssl switches (assuming that the below prerequisites are met).

Prerequisites

• OS: One of Linux x86 (32/64), ARM (32/64), MIPS (32/64), PowerPC (32/64), S390X, SuperH, Microblaze, OpenRISC (ref)
• Nim: https://nim-lang.org/ (built from *devel* branch as of <2018-09-13 Thu>)
• musl library: https://www.musl-libc.org/download.html
• curl and GNU tar are needed on the system for the -d:pcre / -d:libressl / -d:openssl switches to work.

Optional

These optional command-line utilities for binary size optimization will be run automatically one by one, if present.

• strip (from binutils): https://sourceware.org/binutils/docs/binutils/strip.html
• upx: https://github.com/upx/upx

Generating static binary

For this example hello_musl project

1. git clone https://github.com/kaushalmodi/hello_musl
2. cd hello_musl
3. Run nim musl [-d:pcre] [-d:libressl|-d:openssl] <FILE>.nim

Static links with just musl lib

nim musl src/hello_musl.nim

That will generate hello_musl binary in src/ directory.

• file ./src/hello_musl will print:

  src/hello_musl: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), statically linked, stripped
      

• ./src/hello_musl will print:

  Hello, World!
      

Static linking with musl + pcre libs

nim musl -d:pcre src/hello_musl_pcre.nim

That will generate hello_musl_pcre binary in src/ directory.

• file ./src/hello_musl_pcre will print:

  src/hello_musl_pcre: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), statically linked, stripped
      

• ./src/hello_musl_pcre will print:

  Hello, World!
  Bye, World!
      

Static linking with musl + libressl libs

nim musl -d:libressl src/hello_musl_ssl.nim

That will generate hello_musl_ssl binary in src/ directory.

• file ./src/hello_musl_ssl will print:

  src/hello_musl_ssl: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), statically linked, stripped
      

• ./src/hello_musl_ssl will print:

  {"name":"Kaushal Modi","type":"card","url":"https://scripter.co/"}
  {
    "name": "Kaushal Modi",
    "type": "card",
    "url": "https://scripter.co/"
  }
  "Kaushal Modi"
      

Note

Binary built using -d:libressl on RHEL 6.8 is known to crash with just a “Killed” message. But the same, when built on Travis, run fine on RHEL 6.8 (mystery). So a RHEL 6.8 user may look at the slightly less secure option of building using with -d:openssl switch instead.

Static linking with musl + openssl libs

nim musl -d:openssl src/hello_musl_ssl.nim

That will generate hello_musl_ssl binary in src/ directory, and the outputs would be same as those you see for the -d:libressl switch.

Note about compiling with statically linked OpenSSL (-d:openssl)

When building with -d:openssl, a statically linked version of OpenSSL library is first built with the -DOPENSSL_NO_SECURE_MEMORY Configure option, because of an issue with it getting built using MUSL.

This security laxing switch is not added if LibreSSL is used instead (~-d:libressl~)

For your Nim project

• Copy the ~config.nims~ to your Nim project.
• While being the same directory as config.nims, do:

  nim musl <path/to/your/nim/file>             # without static pcre lib linking
  nim musl -d:pcre <path/to/your/nim/file>     # *with* static pcre lib linking
  nim musl -d:libressl <path/to/your/nim/file> # *with* static libressl lib linking
  nim musl -d:openssl <path/to/your/nim/file>  # *with* static openssl lib linking (less secure)
      

References

• https://github.com/nim-lang/Nim/wiki/Using-nimscript-for-configuration
• https://nim-lang.org/docs/nims.html
  • https://nim-lang.org/docs/nimscript.html
• https://hookrace.net/blog/nim-binary-size/#using-the-c-standard-library
• https://www.reddit.com/r/programming/comments/2wk7q6/static_linking_with_nim/corwtl7/

Todo-List

• [ ] Figure out how to have nimble install install the binary generated by nim musl.
• [X] Don’t hard-code the muslGcc const in config.nims
• [X] Not require hello_musl.nimble
  • Currently that is needed just to add the -d:musl and -d:release switches, and then to auto-run strip -s.
  • So to remove dependency on this file, I need to figure out how to get the current foo.nim file name from within the config.nims.
  • Eventual goal is to reuse the same config.nims for all projects. So I cannot hardcode the pkgName as I do in hello_musl.nimble.