On 16 May 2017, at 07:42, Johannes Lundberg <johal...@gmail.com> wrote:
> Gonna answer myself here. Think I found a way.
> Add CFLAGS=-fcolor-diagnostics to env or /etc/src.conf
> Do clean build, that is no -DNO_CLEAN,KERNFAST, etc.
> Makes it a lot easier to find the errors in a 16 threads build output...
> The mystery still remains though, why is color disabled for parallel
> builds?

It’s disabled for two reasons.  The first is aesthetic - some people don’t like 
coloured output.  I’m not going to debate that one.  The other is technical.  
Unlike modern build tools, such as Ninja, bmake’s handling of multithreaded 
output is very bad.  It simply allows each task the same output device, whereas 
ninja gives each parallel job a pipe back to the build process and then merges 
the output itself.  This means that you periodically encounter the case where 
one child process has sent a colour escape sequence to the output and then 
another process sends the next line, giving weird visual effects and reducing 
the utility of colour outputs.

Ideally, we’d solve this by fixing bmake to behave more like a modern build 
tool and:

 - Giving each sub-process its own pipe.
 - Emitting the full compile command for all failed tasks.
 - Displaying only a summary for successful commands

Or we could find someone with the time to spend giving FreeBSD a modern build 
system, which would probably save us 1-2 man years of developer time each year 


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