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Bun: cgroup-aware AvailableParallelism / HardwareConcurrency on Linux

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Re: Bun: cgroup-aware AvailableParallelism / HardwareConcurrency on Linux

#5

Post by lioeters »

jasdfwasd wrote: post #3
saagarjha wrote: post #2

I feel like https://github.com/oven-sh/WebKit/commit/35315978baee84ed1bd... is the more interesting commit tbh

> p = (char*)""; yikes

I thought that was a typo or the forum software removed something, but no - it's a pointer to an empty string literal. If I understand how that works, this creates a null byte (in the read-only memory section of the compiled output?) and points to it. Before this line it checks if p is NULL.

I wonder what is the advantage of doing this? Maybe to make sure that p is an actual pointer, so later code can just make that assumption.

Re: Bun: cgroup-aware AvailableParallelism / HardwareConcurrency on Linux

#6

Post by lokar »

lioeters wrote: post #5
jasdfwasd wrote: post #3

Earlier quoted context omitted.

> p = (char*)""; yikes

I thought that was a typo or the forum software removed something, but no - it's a pointer to an empty string literal. If I understand how that works, this creates a null byte (in the read-only memory section of the compiled output?) and points to it. Before this line it checks if p is NULL. I wonder what is the advantage of doing this? Maybe to make sure that p is an actual pointer, so later code can just make that…

Yeah, it simplifies later code, and is safer in the face of future changes.

Or put another way, it tightens the API/contract of that chunk of code to always return a valid string.

Re: Bun: cgroup-aware AvailableParallelism / HardwareConcurrency on Linux

#9

Post by lioeters »

lokar wrote: post #6
lioeters wrote: post #5

Earlier quoted context omitted.

I thought that was a typo or the forum software removed something, but no - it's a pointer to an empty string literal. If I understand how that works, this creates a null byte (in the read-only memory section of the compiled output?) and points to it. Before this line it checks if p is NULL. I wonder what is the advantage of doing this? Maybe to make sure that p is an actual pointer, so later code can just make that…

Yeah, it simplifies later code, and is safer in the face of future changes. Or put another way, it tightens the API/contract of that chunk of code to always return a valid string.

That makes sense, with that "guard" at the top, the rest of the function can return the pointer anywhere. And I imagine the compiler will ensure the empty string literal is created only once. Good to know!

Re: Bun: cgroup-aware AvailableParallelism / HardwareConcurrency on Linux

#10

Post by himata4113 »

elffjs wrote: post #4

Something from the PR description that I had to look up to understand: "WTF" is "WebKit Template Framework".

I had to take a moment to find out why all primitives in chrome were in the WTF namespace.

WTF is just kinda funny. Seen it used in loggers too log.wtf("this should never happen")

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