A Tutorial on Portable Makefiles • Hacker News Board

Re: A Tutorial on Portable Makefiles

#111

Post by albinofrenchy » Mon, Aug 21, 2017, 9:13 PM UTC

throwaway613834 wrote: post #40

albinofrenchy wrote: post #39

Earlier quoted context omitted.

AFAIK cmake works perfectly fine with relative paths; what breaks?

I don't think it works: https://ofekshilon.com/2016/08/30/cmake-rants/

I thought you meant giving it relative paths in your CMakeLists.txt -- which does work as expected.

> This makes CMake-generated projects almost useless: you cannot source control them or share them in any other way.

Yes, and this is a good thing. I'm surprised anyone would want to do this on a visual studio solution of all things -- managing solution and project file merges in source control is incredibly tedious.

A lot of things about CMake irritate me, but its treatment of out of source build files as purely intermediate is a major plus to me, not a negative.

I could see how this would mess up your use case; but you have to admit your use case is very narrow -- I guess you want to be able to just rename the build folder; if you moved it more than that even the relative path to the source dir would be off -- and the justification for the limitation seems sensible.

Re: A Tutorial on Portable Makefiles

#112

Post by frankzinger » Tue, Aug 22, 2017, 6:11 AM UTC

chubot wrote: post #62

rossy wrote: post #57

Earlier quoted context omitted.

If you have -MD or -MMD in your CFLAGS, GCC (and Clang) will generate the .d files during compilation without you having to add anything else to the Makefile, and without requiring ugly sed magic.

I just tried this, and it seems wrong on two counts: 1) The sed magic is required for adding the dependencies of the .d file itself. For example, if the timestamp of your header changes, it may have acquired new dependencies, and a new .d file has to be generated BEFORE make determines if the .c file is out of date. See: https://www.gnu.org/software/make/manual/html_node/Automatic... The purpose of the sed command is…

There's a -MT flag which does what the sed line does. From the gcc man page:

  Change the target of the rule emitted by
  dependency generation... An -MT option will
  set the target to be exactly the string you
  specify...

So in your example one might do something like

  -MT "$@ $(basename $@).d"

which would output

  main.o main.d : main.c defs.h

for the main.o target.

Re: A Tutorial on Portable Makefiles

#113

Post by JdeBP » Wed, Aug 23, 2017, 11:34 AM UTC

erlehmann_ wrote: post #100

JdeBP wrote: post #98

Earlier quoted context omitted.

I, for one, handle it with a tool that mimics the compiler's preprocessing phase and emits both redo-ifchange information for all of the headers that are used, and redo-ifcreate information for all of the non-existent headers that are looked for during the process. JdeBP %cat test.cpp #include void f() {} JdeBP %/package/prog/cc/command/cpp test.cpp --iapplication . --icompiler-high /usr/local/lib/gcc5/include/c++ --…

I use strace(1) look for stat(2) syscalls that fail with ENOENT. An advantage of this approach is that I do not have to imitate the C preprocessor, so parser differentials can never happen. The following default.o.do file from my blog post [1] handles the case: #!/bin/sh redo-ifchange $2.c strace -e stat,stat64,fstat,fstat64,lstat,lstat64 -f 2>&1 >/dev/null\ gcc $2.c -o $3 -MD -MF $2.deps\ |grep '1 ENOENT'\ |grep '\.…

Just for the record: My personal preference is for Clang and GCC to be instrumented to emit the names of both found and non-existent header files.

Re: A Tutorial on Portable Makefiles

#114

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