Re: bin/40115: make(1) behaviour is inconsistent across parallel and ordinary builds

[christos%zoulas.com@localhost (Christos Zoulas)]

The following reply was made to PR bin/40115; it has been noted by GNATS.

From: christos%zoulas.com@localhost (Christos Zoulas)
To: Aleksej Saushev <asau%inbox.ru@localhost>, gnats-bugs%NetBSD.org@localhost
Cc: gnats-admin%netbsd.org@localhost, netbsd-bugs%netbsd.org@localhost
Subject: Re: bin/40115: make(1) behaviour is inconsistent across parallel and 
ordinary builds
Date: Sun, 7 Dec 2008 10:16:19 -0500

 On Dec 7, 11:02am, asau%inbox.ru@localhost (Aleksej Saushev) wrote:
 -- Subject: Re: bin/40115: make(1) behaviour is inconsistent across parallel 
 
 | christos%zoulas.com@localhost (Christos Zoulas) writes:
 | 
 | >  This is not a bug. When -j is present, make tries to execute multiple
 | >  shell commands in a single shell instance for efficiency. This is not
 | >  very well documented in the man page, but -B gives a hint about it.
 | >  If you want to execute each line in its own shell process, use -B.
 | >  Most shell snippets that don't cd or chdir, benefit from the new way
 | >  of execution.
 | 
 | I'd rather say, it isn't documented at all. The respective parts read:
 | 
 | -B
 |    Try to be backwards compatible by executing a single shell per
 |    command and by executing the commands to make the sources of a
 |    dependency line in sequence.
 | 
 | -j max_jobs
 |    Specify the maximum number of jobs that make may have running at
 |    any one time.  Turns compatibility mode off, unless the B flag is
 |    also specified.
 | 
 | That "try to be backwards compatible by executing a single shell per
 | command" gives only a delicate hint, which is far from obvious. In my
 | opinion "-j" part should mention it explicitly: "All commands associated
 | with [particular? - fix style, please!] target are executed in single
 | shell invocation."
 | 
 | Why is it backwards compatible mode, which is on by default?
 | Why don't make make run commands in single shell invocation
 | and request explicit backward compatibility? Does it break
 | too much code?
 
 pmake was the make front end used by Sprint. If -j was specified, make
 used "customs" a remote execution daemon to fork jobs on different
 machines. It would have been very inefficient and difficult to control
 to execute command by command on the remote system, so I guess they
 chose to execute all the commands for a specified target in one shot.
 
 christos