Re: [PATCH] Fix problem with generation of man/poke.1

[John Darrington]

On Thu, Nov 14, 2019 at 12:34:41PM +0100, Jose E. Marchesi wrote:
     
     Hi John.
     
         ---
          man/Makefile.am | 14 +++++++++-----
          1 file changed, 9 insertions(+), 5 deletions(-)
         
         diff --git a/man/Makefile.am b/man/Makefile.am
         index 1627b1f..30d0319 100644
         --- a/man/Makefile.am
         +++ b/man/Makefile.am
         @@ -23,10 +23,14 @@ MAINTAINERCLEANFILES = $(man_MANS)
          # The man pages depend on the version number.
          common_mandeps = $(top_srcdir)/configure.ac
          
         -# Depend on the source, not the binary; we don't need to regenerate
         -# the binary when any source file changes, only the main one.
         +# Jose writes:
         +##  Depend on the source, not the binary; we don't need to regenerate
         +##  the binary when any source file changes, only the main one.
         +# However, there is no guarantee that the binary will exist, so 
dependence
         +# on the source is appropriate, and help2man is cheap anyway.
     
     You mean "dependence on the object is appropriate"?

Yes.  That's what I meant.  Sorry
     
         +
          # Use -o so that the `missing' program can infer the output file.
          
         -poke.1: $(top_srcdir)/src/poke.c $(common_mandeps)
         -      $(HELP2MAN) -p poke --name="The GNU extensible binary editor" \
         -              $(builddir)/../src/poke -o $@
         +poke.1: $(top_builddir)/src/poke $(common_mandeps)
         + POKEDATADIR=$(abs_top_srcdir)/src $(HELP2MAN) -p poke --name="The
         GNU extensible binary editor" \
         +              $< -o $@
     
     I don't get it.  The man/ subdirectory is recursed by Automake after
     src/ while executing the target `all' so the binary should indeed exist
     at the time the rule is triggered...  

You cannot guarantee that.  Firstly, if the -j flag is passed then you
do not know the order - they could even happen in parallel.  Secondly,
when make sees a rule like :

basedir: src man x y

whilst *most* implementations (when no -j flag is given) process the 
targets from left to right, that is not specified by any standard
(the GNU Make manual doesn't specify)

FWIW: I recommend not using the SUBDIRS feature of automake.  Instead,
use a non recursive makefile system - it's faster and more reliable.
See Peter Miller's paper "Recursive Make Considererd Harmfull".

J'


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