Thanks a lot for the helpfull answers Stuart and Jeremie. On October 9, 2019 11:11:22 AM GMT+02:00, Jeremie Courreges-Anglas <j...@wxcvbn.org> wrote: >On Wed, Oct 09 2019, Christopher Zimmermann <chr...@openbsd.org> wrote: >> On Tue, Oct 08, 2019 at 01:44:14PM +0200, Jeremie Courreges-Anglas >wrote: >>> On Tue, Oct 08 2019, Christopher Zimmermann <madro...@gmerlin.de> >wrote: >>> > On Mon, Oct 07, 2019 at 09:09:50PM +0100, Stuart Henderson wrote: >>> >> On 2019/10/07 21:37, Christopher Zimmermann wrote: >>> >> > How is an arbitrary piece of software supposed to >>> >> > discover /usr/local/include and /usr/local/lib? >>> >> >>> >> The same way it will discover /opt/include and /opt/lib on a >linux box - >>> >> you tell it to look there. >>> > >>> > - What's the preferred way to teach a build system our search >paths ? >>> > - What's the preferred / most portable way for a piece of software >to >>> > discover the search paths? >>> > >>> > Is it pkg-config, $CPATH / $LIBRARY_PATH, autoconf, something >else? >>> >>> Many build systems have support for pkg-config (eg pkg.m4 for >autoconf). >>> autoconf honours (at least) CPPFLAGS/CFLAGS/LDFLAGS. >>> CPATH and LIBRARY_PATH are OCaml idioms AFAIK. >> >> Quite contrary CPATH and LIBRARY_PATH are variables heeded by gcc and >> clang compiler and linker. > >Hah, indeed, I had completely forgotten about this. > >> I did some experiments: >> >> $ echo '#include<bzlib.h>' >incl_test.c >> $ CPATH= cc -E -Wp,-v incl_test.c >/dev/null >> clang -cc1 version 8.0.1 based upon LLVM 8.0.1 default target >amd64-unknown-openbsd6.6 >> #include "..." search starts here: >> #include <...> search starts here: >> /usr/lib/clang/8.0.1/include >> /usr/include >> End of search list. >> incl_test.c:1:9: fatal error: 'bzlib.h' file not found >> #include<bzlib.h> >> ^~~~~~~~~ >> 1 error generated. >> $ CPATH=/usr/local/include cc -E -Wp,-v incl_test.c >/dev/null >> clang -cc1 version 8.0.1 based upon LLVM 8.0.1 default target >amd64-unknown-openbsd6.6 >> #include "..." search starts here: >> #include <...> search starts here: >> /usr/local/include >> /usr/lib/clang/8.0.1/include >> /usr/include >> >> But this is _really_ unexpected: >> >> $ CPATH= echo '#include<bzlib.h>' |cc -E -Wp,-v - >/dev/null > >> clang -cc1 version 8.0.1 based upon LLVM 8.0.1 default target >amd64-unknown-openbsd6.6 >> #include "..." search starts here: >> #include <...> search starts here: >> /usr/local/include >> /usr/X11R6/include >> /usr/lib/clang/8.0.1/include >> /usr/include >> End of search list.nd of search list >> >> This tells me that the preprocessor has a decent idea of our search >> path, but forgets about /usr/local and /usr/X11R6 includes when a >file >> is passed as argument instead of run in a pipe. >> >> The heck why does it do that? > >Your command doesn't do what you think it does. > >> CPATH= echo '#include<bzlib.h>' |cc -E -Wp,-v - >/dev/null > >CPATH is only clobbered for the first command in the pipe, 'echo'. >'cc' >still inherits whatever is in CPATH, and I guess it's set to a custom >value. Did you actually remove CPATH/LIBRARY_PATH from your >/etc/profile? ;)
Well yes, I did indeed, but did not yet reboot. >--8<-- >russell ~/tests$ echo '#include<bzlib.h>' | CPATH= cc -E -Wp,-v - >>/dev/null >clang -cc1 version 8.0.1 based upon LLVM 8.0.1 default target >amd64-unknown-openbsd6.6 >ignoring nonexistent directory "/usr/lib/clang/8.0.1/include" >#include "..." search starts here: >#include <...> search starts here: > /usr/include >End of search list. ><stdin>:1:9: fatal error: 'bzlib.h' file not found >#include<bzlib.h> > ^~~~~~~~~ >1 error generated. >-->8-- > > >>> There's no single answer. >> >> Of course not. >> >>> Can opam simply inject -I/usr/local/include and -L/usr/local/lib in >the >>> dune build system used by ocaml-lmdb? >> >> Since the C compiler/linkers heed CPATH and LIBRARY_PATH, I can >simply >> set those variables to inject the standard search path. >> But why do I even have to do that? The preprocessor seems to know the >> correct search path, but seems to forget it under some circumstances. > >By design our base compilers aren't supposed to look into /usr/local or >/usr/X11R6. Then for a build system is there any way to discover /usr/local/include except guessing? Christopher
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