Use getentropy() instead of /dev/urandom on Emscripten

[kleisauke]

/dev/urandom is usually available on Emscripten, except when using
the special NODERAWFS filesystem backend, which replaces all normal
filesystem access with direct Node.js operations.

Since this filesystem backend directly access the filesystem on the
OS, it is not recommended to depend on /dev/urandom, especially
when trying to run the Wasm binary on OSes that are not Unix-based.

This can be considered a non-functional change, since Emscripten
implements /dev/urandom in the same way as getentropy() when not
linking with -sNODERAWFS.

[rustbot]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @joshtriplett (or someone else) soon.

Please see the contribution instructions for more information.

[kleisauke]

This is ready for review now that libc 0.2.140 was released.

[rustbot]

Hey! It looks like you've submitted a new PR for the library teams!

If this PR contains changes to any rust-lang/rust public library APIs then please comment with @rustbot label +T-libs-api -T-libs to tag it appropriately. If this PR contains changes to any unstable APIs please edit the PR description to add a link to the relevant API Change Proposal or create one if you haven't already. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary.

Examples of T-libs-api changes:

• Stabilizing library features
• Introducing insta-stable changes such as new implementations of existing stable traits on existing stable types
• Introducing new or changing existing unstable library APIs (excluding permanently unstable features / features without a tracking issue)
• Changing public documentation in ways that create new stability guarantees
• Changing observable runtime behavior of library APIs

These commits modify the Cargo.lock file. Random changes to Cargo.lock can be introduced when switching branches and rebasing PRs.
This was probably unintentional and should be reverted before this PR is merged.

If this was intentional then you can ignore this comment.

[ChrisDenton]

lgtm

@bors r+

[bors]

📌 Commit 4d40cdf has been approved by ChrisDenton

It is now in the queue for this repository.

[bors]

⌛ Testing commit 4d40cdf with merge 8e6b904aeb2f7cd2dc46ea94a5390252d1303d9b...

[bors]

💔 Test failed - checks-actions

[kleisauke]

It looks like we need to bump the minimum supported Emscripten version to 2.0.5 for this (which is 2 months newer than 1.39.20), see commit 7b40eb7.

[ChrisDenton]

Ah, ok. Let's try again...

@bors r+

[bors]

📌 Commit 7b40eb7 has been approved by ChrisDenton

It is now in the queue for this repository.

[bors]

⌛ Testing commit 7b40eb7 with merge 1033857...

[bors]

☀️ Test successful - checks-actions
Approved by: ChrisDenton
Pushing 1033857 to master...

[rust-timer]

Finished benchmarking commit (1033857): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	1.2%	[1.2%, 1.2%]	1
Regressions ❌ (secondary)	2.9%	[2.7%, 3.1%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.7%	[-2.7%, -2.7%]	1
All ❌✅ (primary)	1.2%	[1.2%, 1.2%]	1

Cycles

This benchmark run did not return any relevant results for this metric.