================
@@ -286,7 +286,33 @@
clang::analyze_format_string::ParseLengthModifier(FormatSpecifier &FS,
lmKind = LengthModifier::AsInt3264;
break;
case 'w':
- lmKind = LengthModifier::AsWide; ++I; break;
+ ++I;
+ if (I == E) return false;
+ if (*I == 'f') {
+ lmKind = LengthModifier::AsWideFast;
+ ++I;
+ } else {
+ lmKind = LengthModifier::AsWide;
+ }
+
+ if (I == E) return false;
+ int s = 0;
+ while (unsigned(*I - '0') <= 9) {
+ s = 10 * s + unsigned(*I - '0');
+ ++I;
+ }
+
+ // s == 0 is MSVCRT case, like l but only for c, C, s, S, or Z on windows
+ // s != 0 for b, d, i, o, u, x, or X when a size followed(like 8, 16, 32
or 64)
+ if (s != 0) {
+ std::set<int> supported_list {8, 16, 32, 64};
----------------
enh-google wrote:
> So I think we should probably err on the side of specifying all the
> bit-widths we specify in stdint.h.
as a libc maintainer (who happens to have done a survey of the other libcs on
this specific bit of C23 functionality, when zijunzhao was implementing it for
bionic :-) ), i'd argue the opposite: none of bionic, glibc, musl, FreeBSD, and
Apple's fork of FreeBSD libc supports these weird sizes[1]. nor does any
hardware i'm aware of. i'd actually argue that the llvm stdint.h change that
added these types should be reverted[2]. (presumably someone who knows the llvm
code better can check whether it's possible for clang to ever actually define
`__INT48_TYPE__` and its non-power-of-two friends? if there really _is_ such an
architecture, we could at least get a useful code comment in stdint.h out of
it!)
as for the diagnostics, i'd argue (a) it doesn't make sense having this be
libc-specific (like, for example, the existing "do math functions set errno?"
configuration) since every libc in use would have the same "no, we don't
support 48-bit ints" setting and (b) saying "well, 56-bit ints _might_ be a
thing in theory, so we'll punt and leave it to be runtime error" isn't very
helpful in a world where it will always be a runtime error.
___
1. to be fair, a couple of them still don't implement %w at all. at the risk of
making more work for zijunzhao, if you were going to teach clang about
different libc versions, _that_ would at least be useful (for those targets
that include a version in them): "which version of Android/iOS first had %b?"
etc. if i'm using %b but targeting a version that didn't have it, that's a
useful compile-time warning, at least as long as anyone's targeting old-enough
versions. (and, full disclosure: for Android that's the same as %w: they're
both new in this year's release ---
https://android.googlesource.com/platform/bionic/+/HEAD/docs/status.md)
2. personally, i don't feel like the commit message on the change that
introduced this stuff to stdint.h motivated it at all. i suspect if llvm hadn't
still been an academic project back then, that change would never have been
accepted in the first place!
https://github.com/llvm/llvm-project/pull/71771
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