liblibc: Prototype getopt on Linux as taking a mutable argument #25642
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These functions do not modify their arguments, so they does not need mutable pointers. The C prototypes take a constant array of mutable C-strings, but that's a legacy quirk from before C had const (since string literals have type `char *`). The Rust prototypes had `*mut` in the wrong place, anyway: to match the C prototypes, it should have been `*const *mut c_char`. Also fix the one caller of execvp in libstd, which now no longer needs an unsafe cast.
This is a GNU-specific weirdness in its getopt implementation (presumably assuming that the function will be called with a mutable argv from main). Quoting the "conforming to" section of its manpage: "POSIX.2 and POSIX.1-2001, provided the environment variable POSIXLY_CORRECT is set. Otherwise, the elements of argv aren't really const, because we permute them." Since we have no way to enforce that that variable is set in an FFI binding, the safe thing to do is to mark the function as taking a mutable array.
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alexcrichton
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T-libs-api
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Squashed into PR #25641. |
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[This is a followup PR to #25641 and contains that commit: this PR only proposes the second commit that GitHub lists.]
There's a GNU-specific weirdness in its getopt implementation (presumably assuming that the function will be called with a mutable argv from main). Quoting the "conforming to" section of its manpage:
Since we have no way to enforce that that variable is set in an FFI binding, I think the safe thing to do is to mark the function as taking a mutable array.
I'm not sure if this is really the right approach. Should we change the other
getoptprototypes to match, for consistency of compilation? Should we exempt other Linux libcs like Musl?