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BOB: a really simple build tool for single-file C++ sources

Introduction

Do you write a lot of little C++ programs that consist of only one source file? But

  1. you don't want to keep typing long compilation commands to specify include paths, dependencies, preprocessor switches, etc?
  2. you also don't want to write a Makefile or shell script to overcome point 1, as the source is a single file only?

Then BOB may be of interest. It allows you to store build information at the start of the source file, which BOB then parses to construct and execute the compilation command. It supports dependencies based on pkg-config, or the legacy way of specifying include directories, library directories and libraries to link manually.

Usage

The header of your source file is scanned for lines starting with /// (note the space at the end). These lines can contain the following directives:

/// packagedir       <dir>                   (<dir>/lib/pkgconfig is searched)'
/// usepackage       <pkgname>'
/// legacydir        <dir>                   (adds <dir>/include and <dir>/lib)'
/// legacyincludedir <dir>'
/// legacylibrarydir <dir>'
/// uselibrary       <libname>'
/// rpath            <dir>                   (extra rpath to use)'
/// target           executable|sharedlib'
/// outputfile       <filename>'
/// cflags           <flags>                 (may contain `<expr>`)'
/// lflags           <flags>                 (may contain `<expr>`)'

Example

See included example-opengl.cpp

$ bob -n  example-opengl.cpp 
DRY RUN, WOULD EXECUTE:
['g++', '-O2', '-D_GNU_SOURCE=1', '-D_REENTRANT', '-I/usr/include/SDL', '-o', 'example-opengl', 'example-opengl.cpp', '-lSDL', '-lGL']
$ bob example-opengl.cpp
$ ./example-opengl 
Screen resolution: 2560 x 1600
Vendor: NVIDIA Corporation
Renderer: GeForce GTX 560 Ti/PCIe/SSE2
Version: 4.3.0 NVIDIA 319.49
GLSL version: 4.30 NVIDIA via Cg compiler
...

Command-line options

Usage: bob [options] <source-file>

Options:
  -h, --help            show this help message and exit
  -n, --dry-run         Don't actually do anything, just print command line to
                        execute
  -v, --verbose         Verbose output
  -r, --no-rpath        Don't set rpath in executable (default: do set rpath)
  -O OPTIMIZATION_LEVEL, --optimization-level=OPTIMIZATION_LEVEL
                        Optimization level, i.e. -O<value> (default: 2%)
  -g, --debug           Include debug information (default: no debug
                        information)
  -u ENABLED_SWITCHES, --use=ENABLED_SWITCHES
                        Turns the given switch on, always overrides switch
                        directive in source

Switches

There's also rudimentary support for different build configurations, using binary "switches":

/// switch           <name> 0|1              (0|1 value specifies the default)'
/// {<conditional>}  directive ...           (note: <conditional> is eval()ed!)'

Switch names can only contain upper-case letters and numbers. For every enabled switch a -DUSE_<switch> is included in the compile command, which can be used in the source file.

Example

See the included example-switch.cpp:

/// switch READLINE 0
/// {READLINE} uselibrary readline

#include <cstdio>
#ifdef USE_READLINE
#include <readline/readline.h>
#endif

int main()
{
#ifdef USE_READLINE
    char *input = readline("What's your name? "); 
    printf("Hi there, %s!\n", input);
#else
    printf("Hi John Doe!\n");
#endif
}

$ ./bob example-switch.cpp 
$ ./example-switch 
Hi John Doe!
$ ./bob -u READLINE example-switch.cpp 
$ ./example-switch 
What's your name? Paul
Hi there, Paul!