LGTM

This should probably be more similar to the putc test, which writes to a file so that the result can be checked.

LGTM

I like the general idea of having a more thorough test for pthreads as a whole, but it should probably be in a separate file instead of replacing the pthread_join test. I think it would fit better in the pthread_test file.

Every platform we support gets broken occasionally by patches that forget to take it into account. Without buildbots telling us when the platform is broken, then we can't fix it. An example for this would be the arm32 failing to update for several months and our strtol tests breaking on it, leading to this patch: https://reviews.llvm.org/D151935.
For this reason we require anyone adding a new platform to demonstrate their plan for supporting that platform through CI. You can look at the "CI Builders" section on this page for more details: https://libc.llvm.org/porting.html

Ideally we would not like to replace the current optional implementation. Instead we would prefer to modify the current optional so that it supports the features that we need, and only replace it if modification isn't practical. Can you explain why you think that modifying the existing implementation of optional cannot work for your use case?

The patch is fine, but I am confused as to how the str_to_float tests were passing with the high_precision_decimal tests failing, given that str_to_float uses high_precision_decimal.

LGTM

LGTM

address comments, still need to mess with the is_lowest_block and zero_blocks_after_point functions. They aren't strictly necessary, but they do provide significant speed improvements.

updates and cleanup

LGTM

LGTM

LGTM

changed how MPFR is included to support downstream configs in the same way as MPFRUtils

cleanup for all three modes after some testing.

LGTM

LGTM

I'll test this patch on aarch64 to check the float128 support

Abandoned in favor of https://reviews.llvm.org/D150905

LGTM

LGTM

LGTM

LGTM, thank you for adding this!

Currently ryu_long_double_constants is empty, this is because it's 12 megabytes and arcanist complains when I try to upload it. I can add it for testing purposes, or you can generate it yourself with ryu_tablegen.py. It writes to the console so pipe it to a file. You'll also need to set POW10_ADDITIONAL_BITS_TABLE to 120, IDX_SIZE to 128, and MID_INT_SIZE to 320 in ryu_long_double_constants.h.

I agree that optional supporting UInt is good, my question is whether replacing the existing implementation with a completely new one is the best strategy.

Before I review this patch, I want to confirm that this is the right strategy. If the main goal is to support Uint<> in optional is there a way to do that without a complete replacement of optional?

I think you meant to put me as a reviewer instead of the description.

add comment to clarify the variable named "a"

fix issues that came up in testing before landing

LGTM

address comments and fix how types are set up.

move time_t change into separate patch.

address comments

switch to system atof for exception detection.

LGTM with a nit.

remove unnecessary char* initializer for cstring and rename the header to c_string.h to clarify that this isn't related to cstring (the libc++ header).

That's fine, I'll land this for you.

move to LIBC_INLINE

LGTM, thank you for catching this.

address comments

address comments

LGTM

we should probably figure out what the appropriate waitpid errno values are before landing this. It's possible that the syscall returns them as negative numbers, but I haven't tested it yet.

Overall LGTM, though are we sure that having the riscv 64 bit and 32 bit targets is the correct path? On other platforms so far we've separated the 32 bit and 64 bit targets.

LGTM