1881917 - Support building with zero component JSMs in tree until both m-c and c-c migrates all components to ESM

Status: RESOLVED FIXED

(Core :: XPCOM, task)

Description

[Tooru Fujisawa [:arai]]

Bug 1770944 is about to remove the last static component JSMs, and it had to remove some code from xpcom/components/StaticComponents.cpp.in and xpcom/components/gen_static_components.py in order to avoid a compilation error comes from gComponentJSMs being 0-length array.

StaticComponents.cpp:13231:47: error: no matching function for call to 'ArrayLengthHelper'
 13231 |   auto jsms = MakeUnique<nsTArray<nsCString>>(MOZ_ARRAY_LENGTH(gComponentJSMs));
       |                                               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/arai/projects/mozilla-unified/obj/do/dist/include/mozilla/ArrayUtils.h:183:12: note: expanded from macro 'MOZ_ARRAY_LENGTH'
  183 |     sizeof(mozilla::detail::ArrayLengthHelper(array))
      |            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/arai/projects/mozilla-unified/obj/do/dist/include/mozilla/ArrayUtils.h:168:8: note: candidate template ignored: substitution failure [with T = const StringOffset, N = 0]: zero-length arrays are not permitted in C++
  168 | char (&ArrayLengthHelper(T (&array)[N]))[N];

But it's problematic for comm-central where there are still some component JSMs.
The code should be kept until both m-c and c-c migrations finish, and the code should compile even if there's no component JSMs in tree.

Comment 1

[Tooru Fujisawa [:arai]]

Attachment: Bug 1881917 - Support building with zero component JSMs. r?#xpcom-reviewers!

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/20ea3f74f4fe
Support building with zero component JSMs. r=xpcom-reviewers,aiunusov,emilio

Comment 3

[pstanciu]

https://hg.mozilla.org/mozilla-central/rev/20ea3f74f4fe