Introduction to JS

JS is Mozilla's JavaScript engine written in C. JS78 is taken from Firefox.

This package is known to build and work properly using an LFS-11.0 platform.

Package Information

JS78 Dependencies


Autoconf-2.13, ICU-69.1, rustc-1.52.0, and Which-2.21

User Notes: https://wiki.linuxfromscratch.org/blfs/wiki/js78

Installation of JS



Unlike most other packages in BLFS, the instructions below require you to untar firefox-78.13.0esr.tar.xz and change into the firefox-78.13.0 folder.

Extracting the tarball will reset the permissions of the current directory to 0755 if you have permission to do that. If you do this in a directory where the sticky bit is set, such as /tmp it will end with error messages:

tar: .: Cannot utime: Operation not permitted
tar: .: Cannot change mode to rwxr-xr-t: Operation not permitted
tar: Exiting with failure status due to previous errors

This does finish with non-zero status, but it does NOT mean there is a real problem. Do not untar as the root user in a directory where the sticky bit is set - that will unset it.

Install JS by running the following commands:



If you are compiling this package in chroot you must do two things. First, as the root user, ensure that /dev/shm is mounted. If you do not do this, the Python configury will fail with a traceback report referencing /usr/lib/pythonN.N/multiprocessing/synchronize.py. Run:

mountpoint -q /dev/shm || mount -t tmpfs devshm /dev/shm

Second, either as the root user export the $SHELL environment variable using export SHELL=/bin/sh or else prepend SHELL=/bin/sh when running the configure command.

Compiling the C++ code respects $MAKEFLAGS and defaults to 'j1', the rust code will use all processors.

mkdir obj &&
cd    obj &&

CC=gcc CXX=g++ \
../js/src/configure --prefix=/usr            \
                    --with-intl-api          \
                    --with-system-zlib       \
                    --with-system-icu        \
                    --disable-jemalloc       \
                    --disable-debug-symbols  \
                    --enable-readline        &&

To run the JS test suite, issue: make -C js/src check-jstests JSTESTS_EXTRA_ARGS="--timeout 300 --wpt=disabled". It's recommended to redirect the output into a log. Depending on the machine, either ten or fourteen JS tests related to locale and timezone fail, because of an issue with recent versions of ICU-69.1.

To run the JIT test suite, issue: make -C js/src check-jit-test JITTEST_EXTRA_ARGS="--timeout 300". One test may fail.



An issue in the installation process causes any running program which links to JS78 shared library (for example, GNOME Shell) to crash if JS78 is upgraded or reinstalled. To work around this issue, remove the old version of the JS78 shared library before installation:

rm -fv /usr/lib/libmozjs-78.so

Now, as the root user:

make install &&
rm -v /usr/lib/libjs_static.ajs &&
sed -i '/@NSPR_CFLAGS@/d' /usr/bin/js78-config

Command Explanations

CC=gcc CXX=g++: Upstream now prefers clang, override it like other Mozilla packages in BLFS book.

--with-*: These parameters allow the build system to use system versions of the above libraries. These are required for stability.

--enable-readline: This switch enables Readline support in the JS shell.

--disable-jemalloc: This switch disables the internal memory allocator used in JS78. jemalloc is only intended for the Firefox browser environment. For other applications using JS78, if JS78 uses jemalloc, the application may crash as items allocated in jemalloc allocator are freed on system (glibc) allocator.

--disable-debug-symbols: Don't generate debug symbols since they are very large and most users won't need it. Remove it if you want to debug JS78.

rm -v /usr/lib/libjs_static.ajs: Remove a large static library which is not used by any BLFS package.

sed -i '/@NSPR_CFLAGS@/d' /usr/bin/js78-config: Prevent js78-config from using buggy CFLAGS.


Installed Programs: js78 and js78-config
Installed Libraries: libmozjs-78.so
Installed Directories: /usr/include/mozjs-78

Short Descriptions


provides a command line interface to the JavaScript engine


is used to find the JS compiler and linker flags


contains the Mozilla JavaScript API functions

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