Non-consistent behavior regarding emscripten

[FrancoisChastel]

Description of the problem / feature request:

When trying to implement emscripten porting to a C/C++ project, non-consistent errors appears regarding the modification of compiler used with exactly the same parameters.

After coming through a guide concerning the usage of emscripten and some investigation, I am not able to figure out a way to be unlocked at all and I presume it's coming from the poor integration with other compilers.

I get the following exact error :

ERROR: /private/var/tmp/_bazel_root/7eac25f81ba1cb3897eb750dd5c677da/external/openssl/BUILD:1100:1: undeclared inclusion(s) in rule '@openssl//:openssl':
this rule is missing dependency declarations for the following files included by 'external/openssl/openssl/crypto/x509/x_crl.c':

when remplacing inside the emcc.sh from the tutorial, emcc to clang some errors still appears but are related to the code. Switching to other compilers does not make it appear as well.

Bugs: what's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

Implement the tutorial into a project with external dependencies.

What operating system are you running Bazel on?

macOS High Sierre - 10.13.6 (17G2307)

What's the output of bazel info release?

release 0.14.0

Have you found anything relevant by searching the web?

No

Any other information, logs, or outputs that you want to share?

I would like to produce documentation for porting C/C++ big code base using bazel and emscripten in the next few weeks if the project is successful

[FrancoisChastel]

Forgot to mention I found a fix for this problem : .d files are poorly managed with a toolchain using Emscripten.

You need to clean the .d files after the calls of emcc by cleaning what is recommended AND by cleaning absolute paths to the _bazel_root :

find . -name "*.d" -exec sed -i -e "2d" {} \;
find . -name "*.d" -exec sed -i -e "s/xxx///g" {} \;

with xxx the file name of the actual output of your bazel instance, to find it, you need to run bazel info and it should the output_base value.

[hlopko]

Emscripten is not a Bazel supported toolchain, only a topic for tutorial. Please don't use it in production (unless you invest in productionalizing it :) Thanks for understanding.

[nornagon]

What @hlopko said, but if you really like sed and just want to hack something up to get it working, plopping this in emcc.sh worked for me:

find . -name "*.d" -exec sed -i -e 's/^\( *\)\/.*external/\1external/' {} \;