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author | Al Viro <viro@zeniv.linux.org.uk> | 2025-01-23 22:51:04 -0500 |
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committer | Al Viro <viro@zeniv.linux.org.uk> | 2025-01-27 19:25:45 -0500 |
commit | c1feab95e0b2e9fce7e4f4b2739baf40d84543af (patch) | |
tree | 8ca3bca18afaac45263905c50491ae86e99ae636 /Documentation/rust/general-information.rst | |
parent | 5f4e6f7f8b77a3b1fb0005f6e1692475785ae05f (diff) | |
download | lwn-c1feab95e0b2e9fce7e4f4b2739baf40d84543af.tar.gz lwn-c1feab95e0b2e9fce7e4f4b2739baf40d84543af.zip |
add a string-to-qstr constructor
Quite a few places want to build a struct qstr by given string;
it would be convenient to have a primitive doing that, rather
than open-coding it via QSTR_INIT().
The closest approximation was in bcachefs, but that expands to
initializer list - {.len = strlen(string), .name = string}.
It would be more useful to have it as compound literal -
(struct qstr){.len = strlen(string), .name = string}.
Unlike initializer list it's a valid expression. What's more,
it's a valid lvalue - it's an equivalent of anonymous local
variable with such initializer, so the things like
path->dentry = d_alloc_pseudo(mnt->mnt_sb, &QSTR(name));
are valid. It can also be used as initializer, with identical
effect -
struct qstr x = (struct qstr){.name = s, .len = strlen(s)};
is equivalent to
struct qstr anon_variable = {.name = s, .len = strlen(s)};
struct qstr x = anon_variable;
// anon_variable is never used after that point
and any even remotely sane compiler will manage to collapse that
into
struct qstr x = {.name = s, .len = strlen(s)};
What compound literals can't be used for is initialization of
global variables, but those are covered by QSTR_INIT().
This commit lifts definition(s) of QSTR() into linux/dcache.h,
converts it to compound literal (all bcachefs users are fine
with that) and converts assorted open-coded instances to using
that.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'Documentation/rust/general-information.rst')
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