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Author SHA1 Message Date
Daniel Bertalan
c0cf6e3744 CMake: Set -fvisibility-inlines-hidden on ELF platforms
The C++ semantics of `inline` dictate that such functions might be
defined in multiple translation units. As with all other functions, they
must have the same address in all TUs. Because of this, the compiler
emits `inline` functions as weak symbols, which the dynamic linker can
then resolve to the same address everywhere.

This rule is responsible for a significant overhead at startup, as such
lookups happen by name. Namely, 86'000 of the 114'000 by-name symbol
lookups when loading LibWeb can be attributed to this. Most of these
are only ever defined in a single object, making this even more
pointless.

As nothing in our code relies on either ELF symbol interposition rules
or function address equality, we can use the -fvisibility-inlines-hidden
escape hatch, which causes this rule to be disregarded. As the symbols
are now hidden, no load-time symbol lookup is needed. This flag is used
without issues in other large C++ codebases like Chromium and LLVM.

Some relevant light reading, suggested by Nico:
- https://ridiculousfish.com/blog/posts/i-didnt-order-that-so-why-is-it-on-my-bill-episode-1.html
- https://www.cs.dartmouth.edu/~sergey/cs258/ABI/UlrichDrepper-How-To-Write-Shared-Libraries.pdf
- https://blog.llvm.org/2018/11/30-faster-windows-builds-with-clang-cl_14.html
- https://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Dialect-Options.html#index-fvisibility-inlines-hidden
2023-08-12 05:14:20 +02:00
Daniel Bertalan
00b4976f2c Everywhere: Make Lagom build with GCC 13
GCC 13 was released on 2023-04-26. This commit fixes Lagom build errors
when using an updated host toolchain:
- Adds a workaround for a bug in constraint handling, which made LibJS
  fail to compile: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109683
- Silences the new `-Wdangling-reference` diagnostic globally. It
  produces multiple false positives with no clear way to silence them
  without `#pragmas`.
- Silences `-Wself-move` in `RefPtr` tests as GCC 13 adds this
  previously Clang-exclusive warning.
2023-05-02 07:03:57 -04:00
Nico Weber
8f988b7bae Meta: Move more common flags to common_compile_options.cmake
For the most part no behavior change, except that we now pass
-Wno-implicit-const-int-float-conversion and -Wno-literal-suffix
only to clang and gcc each in both lagom and serenity builds,
while we previously passed them to both in lagom builds (and
passed them to one each in serenity builds). The former is
a clang flag, the latter a gcc flag, but since we also use
-Wno-unknown-warning-option it doesn't really matter.
2023-04-18 10:05:49 +02:00
Nico Weber
4aaefeb1d5 Meta: Move some flags to common_compile_options.cmake
No behavior change.
2023-04-17 00:52:21 +02:00
Linus Groh
ee721978f6 Meta: Move compiler flags into standalone CMake files
This way we can have all of them in a single place, similar to how we
structure options added via the serenity_option() macro.
2022-05-14 17:53:06 +02:00