Ubuntu 18.04 needs llvm to build mozjs_sys

[GPHemsley]

When attempting to compile servo on Ubuntu 18.04, I encountered a number of errors when it reached the step of building mozjs_sys:

backend.mk:2160: warning: overriding recipe for target '../dist/system_wrappers/pixman.h'
backend.mk:1278: warning: ignoring old recipe for target '../dist/system_wrappers/pixman.h'
error: unknown argument: '-fno-sized-deallocation'
error: invalid value 'gnu++14' in '-std=gnu++14'
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/Char16.h:190:15: error: unknown type name 'char16_t'
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/Char16.h:194:1: error: C++ requires a type specifier for all declarations
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/Char16.h:194:22: error: use of undeclared identifier 'char16_t'
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/Char16.h:195:1: error: C++ requires a type specifier for all declarations
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/Char16.h:195:15: error: use of undeclared identifier 'char16_t'
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/Char16.h:195:30: error: use of undeclared identifier 'char16_t'
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/Char16.h:196:1: error: C++ requires a type specifier for all declarations
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/Char16.h:196:22: error: use of undeclared identifier 'u'
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/Char16.h:197:1: error: C++ requires a type specifier for all declarations
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/Char16.h:197:22: error: use of undeclared identifier 'u'
/usr/bin/../lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/bits/std_abs.h:101:3: error: unknown type name '__float128'
/usr/bin/../lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/bits/std_abs.h:102:7: error: unknown type name '__float128'
/usr/bin/../lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/stdlib.h:54:12: error: target of using declaration conflicts with declaration already in scope
/usr/bin/../lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/bits/std_abs.h:102:3: note: target of using declaration
/usr/include/stdlib.h:837:12: note: conflicting declaration
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/TypeTraits.h:49:10: error: unknown type name 'constexpr'
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/TypeTraits.h:49:21: error: expected ';' at end of declaration list
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/TypeTraits.h:50:11: error: unknown type name 'T'
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/TypeTraits.h:101:36: error: use of undeclared identifier 'char16_t'
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/TypeTraits.h:182:35: warning: variadic templates are a C++11 extension [-Wc++11-extensions]
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/TypeTraits.h:267:27: warning: rvalue references are a C++11 extension [-Wc++11-extensions]
fatal error: too many errors emitted, stopping now [-ferror-limit=]
error: unknown argument: '-fno-sized-deallocation', err: true
error: invalid value 'gnu++14' in '-std=gnu++14', err: true
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/Char16.h:190:15: error: unknown type name 'char16_t', err: true
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/Char16.h:194:1: error: C++ requires a type specifier for all declarations, err: true
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/Char16.h:194:22: error: use of undeclared identifier 'char16_t', err: true
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/Char16.h:195:1: error: C++ requires a type specifier for all declarations, err: true
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/Char16.h:195:15: error: use of undeclared identifier 'char16_t', err: true
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/Char16.h:195:30: error: use of undeclared identifier 'char16_t', err: true
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/Char16.h:196:1: error: C++ requires a type specifier for all declarations, err: true
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/Char16.h:196:22: error: use of undeclared identifier 'u', err: true
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/Char16.h:197:1: error: C++ requires a type specifier for all declarations, err: true
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/Char16.h:197:22: error: use of undeclared identifier 'u', err: true
/usr/bin/../lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/bits/std_abs.h:101:3: error: unknown type name '__float128', err: true
/usr/bin/../lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/bits/std_abs.h:102:7: error: unknown type name '__float128', err: true
/usr/bin/../lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/stdlib.h:54:12: error: target of using declaration conflicts with declaration already in scope, err: true
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/TypeTraits.h:49:10: error: unknown type name 'constexpr', err: true
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/TypeTraits.h:49:21: error: expected ';' at end of declaration list, err: true
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/TypeTraits.h:50:11: error: unknown type name 'T', err: true
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/TypeTraits.h:101:36: error: use of undeclared identifier 'char16_t', err: true
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/TypeTraits.h:182:35: warning: variadic templates are a C++11 extension [-Wc++11-extensions], err: false
/home/gphemsley/Development/Servo/servo/servo/target/debug/build/mozjs_sys-efce9ed11fb4e734/out/dist/include/mozilla/TypeTraits.h:267:27: warning: rvalue references are a C++11 extension [-Wc++11-extensions], err: false
fatal error: too many errors emitted, stopping now [-ferror-limit=], err: true
thread 'main' panicked at 'Should generate JSAPI bindings OK: ()', libcore/result.rs:1009:5
note: Run with `RUST_BACKTRACE=1` for a backtrace.

One of the pages I found while searching (which I've now misplaced) was about encountering a similar error on macOS, and the apparent fix involved installing llvm through brew.

After finding no other useful solution, I decided to attempt sudo apt-get install llvm-dev. When rerunning the build, I was able to get past the point I used to error at. This seems to suggest that llvm or llvm-dev is a prerequisite for building servo, at least on Ubuntu 18.04. (I didn't have llvm installed, either, so I can't say for sure which one is the dependency.)

The bootstrap and/or README should probably be updated to indicate that.

[CYBAI]

Maybe it's good to send a PR to update the README :)

Ref: https://github.com/servo/servo#on-debian-based-linuxes

[dralley]

This looks like it has been done, https://github.com/servo/servo#on-debian-based-linuxes

Can be closed.

[CYBAI]

Thanks! llvm-dev is added in the readme now!