[libc++] Fix incorrect overflow checking in std::lcm (#96310)

We should have been using __builtin_mul_overflow from the start instead
of adding a manual (and error-prone) check for overflow.

Fix

[libc++] Fix incorrect overflow checking in std::lcm (#96310)

We should have been using __builtin_mul_overflow from the start instead
of adding a manual (and error-prone) check for overflow.

Fixes #96196

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[libc++] Refactor tests to remove uses of std::rand()

This allows running these tests on systems that do not support std::rand().

[libc++] Remove the c++98 Lit feature from the test suite

C++98 and C++03 are effectively aliases as far as Clang is concerned.
As such, allowing both std=c++98 and std=c++03 as Lit parameters is
ju

[libc++] Remove the c++98 Lit feature from the test suite

C++98 and C++03 are effectively aliases as far as Clang is concerned.
As such, allowing both std=c++98 and std=c++03 as Lit parameters is
just slightly confusing, but provides no value. It's similar to allowing
both std=c++17 and std=c++1z, which we don't do.

This was discovered because we had an internal bot that ran the test
suite under both c++98 AND c++03 -- one of which is redundant.

Differential Revision: https://reviews.llvm.org/D80926

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Support tests in freestanding

Summary:
Freestanding is *weird*. The standard allows it to differ in a bunch of odd
manners from regular C++, and the committee would like to improve that
situation. I

Support tests in freestanding

Summary:
Freestanding is *weird*. The standard allows it to differ in a bunch of odd
manners from regular C++, and the committee would like to improve that
situation. I'd like to make libc++ behave better with what freestanding should
be, so that it can be a tool we use in improving the standard. To do that we
need to try stuff out, both with "freestanding the language mode" and
"freestanding the library subset".

Let's start with the super basic: run the libc++ tests in freestanding, using
clang as the compiler, and see what works. The easiest hack to do this:

In utils/libcxx/test/config.py add:

self.cxx.compile_flags += ['-ffreestanding']

Run the tests and they all fail.

Why? Because in freestanding `main` isn't special. This "not special" property
has two effects: main doesn't get mangled, and main isn't allowed to omit its
`return` statement. The first means main gets mangled and the linker can't
create a valid executable for us to test. The second means we spew out warnings
(ew) and the compiler doesn't insert the `return` we omitted, and main just
falls of the end and does whatever undefined behavior (if you're luck, ud2
leading to non-zero return code).

Let's start my work with the basics. This patch changes all libc++ tests to
declare `main` as `int main(int, char**` so it mangles consistently (enabling us
to declare another `extern "C"` main for freestanding which calls the mangled
one), and adds `return 0;` to all places where it was missing. This touches 6124
files, and I apologize.

The former was done with The Magic Of Sed.

The later was done with a (not quite correct but decent) clang tool:

https://gist.github.com/jfbastien/793819ff360baa845483dde81170feed

This works for most tests, though I did have to adjust a few places when e.g.
the test runs with `-x c`, macros are used for main (such as for the filesystem
tests), etc.

Once this is in we can create a freestanding bot which will prevent further
regressions. After that, we can start the real work of supporting C++
freestanding fairly well in libc++.

<rdar://problem/47754795>

Reviewers: ldionne, mclow.lists, EricWF

Subscribers: christof, jkorous, dexonsmith, arphaman, miyuki, libcxx-commits

Differential Revision: https://reviews.llvm.org/D57624

llvm-svn: 353086

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Update more file headers across all of the LLVM projects in the monorepo
to reflect the new license. These used slightly different spellings that
defeated my regular expressions.

We understand that

Update more file headers across all of the LLVM projects in the monorepo
to reflect the new license. These used slightly different spellings that
defeated my regular expressions.

We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.

Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.

llvm-svn: 351648

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Change (void) casts to TEST_IGNORE_NODISCARD, as requested by Eric. Reviewed as https://reviews.llvm.org/D40065

llvm-svn: 318804

[libcxx] [test] Untabify, NFC.

llvm-svn: 309464

Resolve integer overflow warnings in GCD and LCM tests

lcm.pass.cpp:
19: Update headers to that actually used in the test.
41: test0 was triggering narrowing warnings for all callers, because the
in

Resolve integer overflow warnings in GCD and LCM tests

lcm.pass.cpp:
19: Update headers to that actually used in the test.
41: test0 was triggering narrowing warnings for all callers, because the
inputs were always ints, but some of the explicit template arguments were
smaller than that. Instead, have this function accept ints and static_cast
explicitly to the types we want before calling std::lcm.
47: Replace unnecessary ternary.
55: Use foo_t instead of typename foo<>::type
111/116: intX_t were not std::qualified but only <cfoo> headers were included.
141: C1XX has a bug where it interprets 2147483648 as unsigned int. Then the
negation trips "negation of unsigned value, result still unsigned" warnings.
Perma-workaround this issue by saying INT_MIN, which better documents the
intended behavior and avoids triggering warnings on C1XX.

gcd.pass.cpp:
Same changes as lcm.pass.cpp but for GCD.

llvm-svn: 302472

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Make lcm/gcd work better in edge cases. Fixes a UBSAN failure.

llvm-svn: 294779

Temporarily disable the LCM/GCD tests under UBSAN.

llvm-svn: 294417

Add some tests to verify that we implement LWG#2837 correctly. No functional change.

llvm-svn: 294194

Fix unused parameters and variables

llvm-svn: 290459

[libcxx] [test] D27027: Strip trailing whitespace.

llvm-svn: 287829

Implement LCM and GCD for C++17. Same code as for Library Fundamentals TS.

llvm-svn: 276751