Hello Peter, Peter Johansson <troj...@gmail.com> writes:
> On 4/22/2018 1:13 AM, Mathieu Lirzin wrote: >> Hello Reuben, >> >> Reuben Thomas <r...@sc3d.org> writes: >> >>> In the manual, we are given the following pattern for using help2man >>> without breaking make distcheck: >>> >>> foo.1: foo.c $(top_srcdir)/configure.ac >>> $(MAKE) $(AM_MAKEFLAGS) foo$(EXEEXT) >>> help2man --output=foo.1 ./foo$(EXEEXT) >>> >>> The problem is that with make -j this can result in two attempts to >>> make a library in parallel (suppose that we have: >>> >>> foo_LDADD = libfoo.la >>> lib_LTLIBRARIES = libfoo.la >>> >>> ). This can fail, and in any case is wasteful. >> Have you identified the reason why this can fail? because > > One problem is that the rule for foo.1 can be triggered before > foo.$(EXEEXT) exists and the rule needs foo.$(EXEEXT) or help2man will > fail. In a -j1 build this is never a problem as binaries are built > before man pages. with the ‘$(MAKE) $(AM_MAKEFLAGS) foo$(EXEEXT)’ recipe line, normally this ensures that the ‘foo$(EXEEXT)’ is built at least once. My question was about understanding why building a program/library twice may end up in a failure in a parallel context. The answer from Reuben was that since compilation is not thead safe when for example deleting shared temporary files, then concurrent processes might impact each other. > When the 'missing' script changed behaviour in Automake 1.13 (and > became useless imvho), we changed the rule in one project so foo.1 > depended on foo.$(EXEEXT) but not if we are 1) building from a tarball > and 2) foo.$(EXEEXT) exists. > > http://dev.thep.lu.se/svndigest/browser/trunk/man/Makefile.am This is an alternative solution which is used by GNU Hello too. I remember some people not being fond of this approach because of its AM_MAINTAINER_MODE spirit [1]. [1] https://www.gnu.org/software/automake/manual/html_node/maintainer_002dmode.html Thanks for your feedback. -- Mathieu Lirzin GPG: F2A3 8D7E EB2B 6640 5761 070D 0ADE E100 9460 4D37
