yihanaa added inline comments.
================
Comment at: clang/lib/Sema/SemaChecking.cpp:433
+
+ llvm::StringRef getFormatSpecifier(QualType T) {
+ if (auto *BT = T->getAs<BuiltinType>()) {
----------------
rsmith wrote:
> rsmith wrote:
> > aaron.ballman wrote:
> > > yihanaa wrote:
> > > > I think this is better maintained in "clang/AST/FormatString.h". For
> > > > example analyze_printf::PrintfSpecifier can get format specifier, what
> > > > do you all think about?
> > > +1 to this suggestion -- my hope is that we could generalize it more then
> > > as I notice there are missing specifiers for things like intmax_t,
> > > size_t, ptrdiff_t, _Decimal types, etc. Plus, that will hopefully make it
> > > easier for __builtin_dump_struct to benefit when new format specifiers
> > > are added, such as ones for printing a _BitInt.
> > I am somewhat uncertain: every one of these is making arbitrary choices
> > about how to format the value, so it's not clear to me that this is general
> > logic rather than something specific to `__builtin_dump_struct`. For
> > example, using `%f` rather than one of the myriad other ways of formatting
> > `double` is somewhat arbitrary. Using `%s` for any `const char*` is
> > *extremely* arbitrary and will be wrong and will cause crashes in some
> > cases, but it may be the pragmatically correct choice for a dumping
> > utility. A general-purpose mechanism would use `%p` for all kinds of
> > pointer.
> >
> > We could perhaps factor out the formatting for cases where there is a clear
> > canonical default formatting, such as for integer types and probably `%p`
> > for pointers, then call that from here with some special-casing, but
> > without a second consumer for that functionality it's really not clear to
> > me what form it should take.
> I went ahead and did this, mostly to match concurrent changes to the old
> implementation. There are a few cases where our existing "guess a format
> specifier" logic does the wrong thing for dumping purposes, which I've
> explicitly handled -- things like wanting to dump a `char` / `signed char` /
> `unsigned char` member as a number rather than as a (potentially
> non-printable or whitespace) character.
When I was patching that old implementation, I found that for uint8_t, int8_t,
Clang's existing "guess a format specifier" logic would treat the value as an
integer, but for unsigned char, signed char, char types, it would Treat it as a
character, please look at this example ( https://godbolt.org/z/ooqn4468T ), I
guess this existing logic may have made some special judgment.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D124221/new/
https://reviews.llvm.org/D124221
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