Hm, it didn't really work out that simple. It broke the build as seen in the CI. I had to put back the explicit $(MANPAGE): rule in src/Makefile.am, which makes the change less neat ... testing this out now.

Coverage increased (+0.4%) to 73.834% when pulling fa39432 on bagder/make-build-docs-from-src into 8621b61 on master.

With the current diff, there are still two ways building curl.1: SUBDIRS and the $(MANPAGE): rule in src/Makefile.am.

To avoid having two ways to archive one goal, I tried to come up with an alternative implementation of the $(MANPAGE): rule that ensures curl.1 is rebuild on dependency changes but can only think of solutions requiring helper Makefiles :(

Yeah, that makes me nervous about this change. Mac OS has gnu make and we have no BSD machines in the CI setup...

I tried having a /src/hugehelp/Makefile.am building all the dependencies for tool_hugehelp.c, but in that place, I do not have paths to the curl.1 dependencies available ($(DPAGES) $(OTHERPAGES) Makefile.inc do not contain paths, only filenames). So this does not work as well.

Thus we can only build curl.1 from /docs/cmdline-opts and /src depends on /docs. Automake cannot model this, since /docs is not a subdir of /src.

Is this pre-build code generation of curl.1 a good idea at all? It somehow mixes maintainer jobs and user jobs. I think there are two clean ways to code generation: either generate at build time by the user or pre-generate for the user. The first way does not work if Perl should not be required. The other way means duplication in the git repo and a maintainer script to generate curl.1. If we have a CI script checking that all generated code is up-to-date, I think this is a good solution.

Assuming pre-build code generation is a good idea, as far as I can see, the only proper way is to move the command line tool documentation into /src/docs

Is this pre-build code generation of curl.1 a good idea at all?

You mean if it is sensible to allow people to build curl from source without requiring perl? Or alternatively, rewrite gen.pl in another language. I think it is worth it mostly for the Windows people, as they're usually the ones least likely to have perl around already.

the only proper way is to move the command line tool documentation into /src/docs

How would that make things better? I don't have any formal objections to that if it means an improved build setup.

You mean if it is sensible to allow people to build curl from source without requiring perl?

I mean half-done code generation of curl.1, that is part of the main build system but ships a pre-build file curl.1 that is not built with the first make but built again when doing something like make && make clean && make. I think any file should either be shipped and fixed or be generated by the build system.

How would that make things better?

/src/Makefile.am gets SUBDIRS = docs and everything from /docs/cmdline-opts moves into /src/docs, causing cd src/docs && make to update /src/docs/curl.1. /src/docs/curl.1 is only updated when necessary and can be pre-generated in the tarball.

This way, the commandline tool is rebuild, if any of the .d files changes because automake's SUBDIRS allows a clean recursive dependency setup.

Won't it still have exactly the same challenges as now, with a file that can't get updated if perl is missing and shouldn't get updated if newer than its dependencies and the problem with non-gnu make on in-tree vs out-of-tree builds?

I don't see why docs/ is better than ../docs for the Makefile.

repushed the same patch again to have it tested on the updated CI distcheck which also does an out-of-tree-build

I don't see why docs/ is better than ../docs for the Makefile.

From the CI failure log of the commit in this PR without the explicit rule, where curl.1 was not available when /src/tool_hugehelp.c was build I think, external dirs in SUBDIRS like ../docs do not work.

external dirs in SUBDIRS like ../docs

The problem there is that we're solving the problem in two different Makefiles, it won't matter if the other makefile is in docs/ or in ../docs. Neither is "external", but both are separate from the one in src/.

If we would merge the generation of curl.1 and the generation hugehelp.c into the same makefile, things would be much cleaner!

Coverage increased (+0.01%) to 73.793% when pulling f1ec13d on bagder/make-build-docs-from-src into 0feb762 on master.

SUBDIRS does indeed work for external directories, such as ../docs

I was having another look into https://travis-ci.org/curl/curl/builds/244466563 (diff: 8621b61...d458a9d), which should work. It turns out that tool_hugehelp.c is built before any of the SUBDIRS because it is in BUILT_SOURCES.

When I now apply 8621b61...d458a9d and remove BUILT_SOURCES = tool_hugehelp.c from src/Makefile.am, my build works fine. This is supported by the documentation, stating:

Moreover, all built sources do not necessarily have to be listed in BUILT_SOURCES. For instance, a generated .c file doesn’t need to appear in BUILT_SOURCES (unless it is included by another source), because it’s a known dependency of the associated object.

Thanks! I committed your change now and pushed to verify the CI likes this.

Coverage decreased (-0.01%) to 73.781% when pulling bcc1c42 on bagder/make-build-docs-from-src into 60c655a on master.

LGTM. This now removes the second way of building curl.1, which was my main point in #1590, in a minimal way.

Regarding other discussion:

• I like the idea of not requring perl for the build, but I don't think there is another scriping laguage to replace it. So curl.1 should be shipped. Maybe at some point, we can pre-generate and check-in curl.1 to keep code generation separate from the user's build system.
• The make process in docs can be simplified a lot if we move docs/curl.1 to docs/cmdline-opts/curl.1, where all it's dependencies are. But this is an independent follow-up.

Maybe at some point, we can pre-generate and check-in curl.1 to keep code generation separate from the user's build system

That's also complicated since we want users who download the tarball to be able to write patches, improve things and be able to regenerate the man page as well to see how their local changes end up looking...

The make process in docs can be simplified a lot if we move docs/curl.1 to docs/cmdline-opts/curl.1, where all it's dependencies are. But this is an independent follow-up.

Yeah, we might as well do that...

Now I've also verified that this PR builds fine on these setups using the default (non-GNU) make:

• FreeBSD in-tree build
• FreeBSD out-of-tree build

Coverage increased (+0.01%) to 73.823% when pulling de769c0 on bagder/make-build-docs-from-src into 922f800 on master.

Thanks for all the help on this @webmaster128!