Include files are not linked at /usr/local/include or /usr/include

[watjurk]

Mac: M1 Apple Silicon, BigSur: 11.2.1
Brew: Homebrew 3.0.1-116-g3ff5795

I don't know if this is intended or not but /usr/local/include and /usr/include does not exist on my system. Brew don't care and the only include path with brew installed formulas is at /opt/homebrew/include.

Is there any way to get brew to "link" includes at /usr/local/include or /usr/include ?

Thanks !

[Bo98]

This is intentional for Apple Silicon.

Is there any way to get brew to "link" includes at /usr/local/include or /usr/include ?

brew does not support doing this. What issue are you having that makes you feel like you need this?

[Syzygies]

I'll describe an issue that brought me to this discussion. I do not need help with a particular issue; one can find workarounds each time. I would like to understand a "once and for all" solution.

I maintain a programming language zoo, and many of these builds take place outside Homebrew, but can take advantage of libraries provided most easily by Homebrew. I am at the moment setting up three Macs at once, in both flavors, and working around the M1 differences.

With some tweaking, one can base a native M1 build of Idris2 on Racket's native M1 build of Chez Scheme. The Idris2 build requires gmp. The build uses /usr/bin/cc which knows about /usr/local/include but not /opt/homebrew/include. One needs to set the CPATH environment variable on an M1 Mac, but not on an Intel Mac.

I have a reasonable expectation that external builds should be able to find Homebrew-installed libraries on either M1 or Intel Macs, without per-build intervention. eval $(${HOMEBREW_PREFIX}/bin/brew shellenv) does not suffice. What am I missing?

(An aside, definitely not worth its own thread, but why does brew shellenv put a trailing colon on MANPATH but not PATH or INFOPATH? I spent twenty minutes thinking I was being clumsy; I find there's a very thin line between understanding my code and falling off the cliff, so I chase everything like this. Is there a reason for this lack of parallelism in the code, or should I provide a pull request to remove that character?)

[carlocab]

I have a reasonable expectation that external builds should be able to find Homebrew-installed libraries on either M1 or Intel Macs, without per-build intervention. eval $(${HOMEBREW_PREFIX}/bin/brew shellenv) does not suffice. What am I missing?

I guess the difficulty is that build systems often defy reasonable expectations. Not because build system developers like being difficult (although there are many times where it seems like they do): the issue is that different users often have mutually exclusive expectations, all of which could be deemed reasonable depending on the context.

If you don't want to use processor-dependent build directives, you can always unconditionally add $(brew --prefix)/include to your CPATH (or the appropriate equivalent to CFLAGS/CXXFLAGS/CPPFLAGS) and -L$(brew --prefix)/lib to your LDFLAGS (or whatever is the equivalent of these for the build system you use). These will resolve to the correct values as long as you're using Homebrew-provided libraries.

why does brew shellenv put a trailing colon on MANPATH but not PATH or INFOPATH?

Because the semantics of MANPATH are different than that of PATH (and perhaps INFOPATH, but I haven't checked this). A trailing : in MANPATH means "append the default MANPATH specified by the system configuration files. A trailing : in PATH means append the current working directory to PATH, which isn't always a good idea.

[andrews05]

I ran into this issue when trying to build an existing program that relied on libpng. In addition to importing <png.h>, the make file used -lpng to link to the library. Under Intel, I just did brew install libpng and then it all just worked when I ran make.
Under M1, I ended up adding the following lines to my profile in order to get it to work:

export CPATH="$HOMEBREW_PREFIX/include:$CPATH"
export LIBRARY_PATH="$HOMEBREW_PREFIX/lib:$LIBRARY_PATH"

Is there a reason the homebrew shellenv doesn't/shouldn't set these itself? I wouldn't expect it to set CFLAGS or similar, but these paths certainly seem reasonable.

[pinheadmz]

I am working with this issue as well after upgrading and migrating. I work on a few nodejs projects that use node-gyp to build native addons to nodejs. It's super inconvenient to add compiler flags to each of those dependencies' binding.gyp files. If I could add something like export CFLAGS -L$(brew --prefix)/lib to my ~/.bash_profile script I would be ok with that, but I dont think that will work

[carlocab]

Why won't it work?