================
@@ -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};
----------------
AaronBallman wrote:
Thanks for the feedback! I did some research of my own to see what the
landscape looks like and here's what I found.
1) Support for these types came in
https://github.com/llvm/llvm-project/commit/55c9877b664c1bc6614ad588f376ef41fe6ab4ca
and there was no discussion on the patch
(https://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20091109/023777.html)
before it landed with post-commit review saying it looked good
(https://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20091116/024219.html)
and no justification beyond wanting a generalized algorithm.
2) There is hardware which supports 48-bit ints
(https://en.wikipedia.org/wiki/48-bit_computing), 36-bit ints
(https://en.wikipedia.org/wiki/36-bit_computing), 24-bit ints
(https://en.wikipedia.org/wiki/24-bit_computing), etc. A lot of it is older
hardware, but as examples, x86-64 uses a 48-bit addressing scheme, OpenCL
supports intrinsics for 24-bit multiplication, UniSys has a 36-bit system they
were selling as of 2015...
3) There's not evidence people are using stdint.h to serve those needs. For
example:
https://sourcegraph.com/search?q=context:global+int48_t+-file:.*clang.*+-file:.*stdint.*+-file:.*int48_t.*&patternType=standard&sm=1&groupBy=repo
shows that most uses are either a custom C++ data type, use of an underlying
non-basic int type, or bit-fields. I don't think I spotted a single use of
`int48_t` that came from stdint.h.
https://sourcegraph.com/search?q=context:global+int24_t+-file:.*clang.*+-file:.*stdint.*+-file:.*int24_t.*&patternType=standard&sm=1&groupBy=repo
shows similarly for `int24_t`.
4) The code which defines the underlying macros used by stdint.h is here:
https://github.com/llvm/llvm-project/blob/29a0f3ec2b47630ce229953fe7250e741b6c10b6/clang/lib/Frontend/InitPreprocessor.cpp#L220
and it uses `TargetInfo::getTypeWidth()` to determine the width generically.
We have no targets
(https://github.com/llvm/llvm-project/tree/main/clang/lib/Basic/Targets) which
define bit widths other than 8, 16, 32, 64, or 128. So Clang itself doesn't
support those odd types yet.
Based on this and your details above, I think we should ignore these odd types
for format strings on the assumption they're just not used. As for removing
them from `stdint.h`, I think that is reasonable to explore given that we have
no targets defining those widths (and so we should never be defining those
macros to begin with); the algorithm remains general, we just drop the extra
cruft from stdint.h. I don't think this should cause any issues.
CC @jrtc27 @jyknight for some extra opinions.
https://github.com/llvm/llvm-project/pull/71771
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