nodejs can't be built with python3 and ninja

[dylanaraps]

• Node Version: v13.10.1
• Platform: Linux KISS 5.5.6-cat Make 0.6.x work node-gyp#1 SMP Mon Feb 24 18:18:34 EET 2020 x86_64 GNU/Linux
• Compiler:

Using built-in specs.
COLLECT_GCC=/usr/bin/cc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-musl/10.0.1/lto-wrapper
Target: x86_64-pc-linux-musl
Configured with: ../gcc/configure --prefix=/usr --disable-multilib --disable-symvers --disable-libmpx --disable-libmudflap --disable-libsanitizer --disable-werror --disable-fixed-point --disable-libstdcxx-pch --disable-nls --without-included-gettext --enable-checking=release --mandir=/usr/share/man --infodir=/usr/share/info --with-system-zlib --enable-__cxa_atexit --enable-default-pie --enable-default-ssp --enable-shared --enable-threads --enable-tls --enable-languages=c,c++ --build=x86_64-pc-linux-musl --disable-bootstrap
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 10.0.1 20200301 (experimental) (GCC)

• Module: nodejs

Nodejs fails to build with Python3 when using '--ninja'.

Node.js configure: Found Python 3.8.2...
INFO: configure completed successfully
ninja: invalid pool depth '1.4507365226745605'

It seems as though there's a missing Python 3 fix in node-gyp. Here's a patch to fix the issue:

diff --git a/tools/gyp/pylib/gyp/generator/ninja.py b/tools/gyp/pylib/gyp/generator/ninja.py
index d5006bf84a..33e1c98b2a 100644
--- a/tools/gyp/pylib/gyp/generator/ninja.py
+++ b/tools/gyp/pylib/gyp/generator/ninja.py
@@ -1786,7 +1786,7 @@ def GetDefaultConcurrentLinks():
           if not match:
             continue
           # Allow 8Gb per link on Linux because Gold is quite memory hungry
-          return max(1, int(match.group(1)) / (8 * (2 ** 20)))
+          return max(1, int(match.group(1)) // (8 * (2 ** 20)))
     return 1
   elif sys.platform == 'darwin':
     try:

More information here: kisslinux/repo#167 (comment)

[michaelforney]

Just to add some context here, the error only occurs with samurai (an alternative ninja implementation), since it checks that the pool depth string could be completely converted to integer, while ninja itself accepts with any string that has an integer prefix.

It doesn't make sense to have a pool with a fractional depth, so gyp shouldn't be outputting a line like depth = 1.4507365226745605.

This is not an issue with Python 2, since it does integer division. Python 3, on the other hand, returns a floating point value.

In upstream gyp, this was fixed in ab4aca86. I'm not sure how much node-gyp has diverged from gyp, but I believe that commit probably has some additional fixes, other than the one @dylanaraps posted above.

[targos]

Thanks for the reference. I'm going to look into porting https://chromium.googlesource.com/external/gyp/+/ab4aca868d68b9de9b20a9991bbbb5e78ab48a30%5E! to our gyp fork later this week.

[targos]

Opened nodejs/gyp-next#11

[juanarbol]

@targos can we close this issue?

[targos]

The bug is fixed in gyp-next but wasn't backported to nodejs/node yet. Let's keep this open.