This completes the implementation of P1091R3 and P1381R1.
This patch allow the capture of structured bindings
both for C++20+ and C++17, with extension/compat warning.
In addition, capturing an anonymous union member,
a bitfield, or a structured binding thereof now has a
better diagnostic.
We only support structured bindings - as opposed to other kinds
of structured statements/blocks. We still emit an error for those.
In addition, support for structured bindings capture is entirely disabled in
OpenMP mode as this needs more investigation - a specific diagnostic indicate the feature is not yet supported there.
Note that the rest of P1091R3 (static/thread_local structured bindings) was already implemented.
at the request of @shafik, i can confirm the correct behavior of lldb wit this change.
Fixes https://github.com/llvm/llvm-project/issues/54300
Fixes https://github.com/llvm/llvm-project/issues/54300
Fixes https://github.com/llvm/llvm-project/issues/52720
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D122768
This completes the implementation of P1091R3 and P1381R1.
This patch allow the capture of structured bindings
both for C++20+ and C++17, with extension/compat warning.
In addition, capturing an anonymous union member,
a bitfield, or a structured binding thereof now has a
better diagnostic.
We only support structured bindings - as opposed to other kinds
of structured statements/blocks. We still emit an error for those.
In addition, support for structured bindings capture is entirely disabled in
OpenMP mode as this needs more investigation - a specific diagnostic indicate the feature is not yet supported there.
Note that the rest of P1091R3 (static/thread_local structured bindings) was already implemented.
at the request of @shafik, i can confirm the correct behavior of lldb wit this change.
Fixes https://github.com/llvm/llvm-project/issues/54300
Fixes https://github.com/llvm/llvm-project/issues/54300
Fixes https://github.com/llvm/llvm-project/issues/52720
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D122768
I went over the output of the following mess of a command:
`(ulimit -m 2000000; ulimit -v 2000000; git ls-files -z | parallel --xargs -0 cat | aspell list --mode=none --ignore-case | grep -E '^[A-Za-z][a-z]*$' | sort | uniq -c | sort -n | grep -vE '.{25}' | aspell pipe -W3 | grep : | cut -d' ' -f2 | less)`
and proceeded to spend a few days looking at it to find probable typos
and fixed a few hundred of them in all of the llvm project (note, the
ones I found are not anywhere near all of them, but it seems like a
good start).
Reviewed By: kadircet
Differential Revision: https://reviews.llvm.org/D130826
Without this patch, clang will not wrap in an ElaboratedType node types written
without a keyword and nested name qualifier, which goes against the intent that
we should produce an AST which retains enough details to recover how things are
written.
The lack of this sugar is incompatible with the intent of the type printer
default policy, which is to print types as written, but to fall back and print
them fully qualified when they are desugared.
An ElaboratedTypeLoc without keyword / NNS uses no storage by itself, but still
requires pointer alignment due to pre-existing bug in the TypeLoc buffer
handling.
---
Troubleshooting list to deal with any breakage seen with this patch:
1) The most likely effect one would see by this patch is a change in how
a type is printed. The type printer will, by design and default,
print types as written. There are customization options there, but
not that many, and they mainly apply to how to print a type that we
somehow failed to track how it was written. This patch fixes a
problem where we failed to distinguish between a type
that was written without any elaborated-type qualifiers,
such as a 'struct'/'class' tags and name spacifiers such as 'std::',
and one that has been stripped of any 'metadata' that identifies such,
the so called canonical types.
Example:
```
namespace foo {
struct A {};
A a;
};
```
If one were to print the type of `foo::a`, prior to this patch, this
would result in `foo::A`. This is how the type printer would have,
by default, printed the canonical type of A as well.
As soon as you add any name qualifiers to A, the type printer would
suddenly start accurately printing the type as written. This patch
will make it print it accurately even when written without
qualifiers, so we will just print `A` for the initial example, as
the user did not really write that `foo::` namespace qualifier.
2) This patch could expose a bug in some AST matcher. Matching types
is harder to get right when there is sugar involved. For example,
if you want to match a type against being a pointer to some type A,
then you have to account for getting a type that is sugar for a
pointer to A, or being a pointer to sugar to A, or both! Usually
you would get the second part wrong, and this would work for a
very simple test where you don't use any name qualifiers, but
you would discover is broken when you do. The usual fix is to
either use the matcher which strips sugar, which is annoying
to use as for example if you match an N level pointer, you have
to put N+1 such matchers in there, beginning to end and between
all those levels. But in a lot of cases, if the property you want
to match is present in the canonical type, it's easier and faster
to just match on that... This goes with what is said in 1), if
you want to match against the name of a type, and you want
the name string to be something stable, perhaps matching on
the name of the canonical type is the better choice.
3) This patch could expose a bug in how you get the source range of some
TypeLoc. For some reason, a lot of code is using getLocalSourceRange(),
which only looks at the given TypeLoc node. This patch introduces a new,
and more common TypeLoc node which contains no source locations on itself.
This is not an inovation here, and some other, more rare TypeLoc nodes could
also have this property, but if you use getLocalSourceRange on them, it's not
going to return any valid locations, because it doesn't have any. The right fix
here is to always use getSourceRange() or getBeginLoc/getEndLoc which will dive
into the inner TypeLoc to get the source range if it doesn't find it on the
top level one. You can use getLocalSourceRange if you are really into
micro-optimizations and you have some outside knowledge that the TypeLocs you are
dealing with will always include some source location.
4) Exposed a bug somewhere in the use of the normal clang type class API, where you
have some type, you want to see if that type is some particular kind, you try a
`dyn_cast` such as `dyn_cast<TypedefType>` and that fails because now you have an
ElaboratedType which has a TypeDefType inside of it, which is what you wanted to match.
Again, like 2), this would usually have been tested poorly with some simple tests with
no qualifications, and would have been broken had there been any other kind of type sugar,
be it an ElaboratedType or a TemplateSpecializationType or a SubstTemplateParmType.
The usual fix here is to use `getAs` instead of `dyn_cast`, which will look deeper
into the type. Or use `getAsAdjusted` when dealing with TypeLocs.
For some reason the API is inconsistent there and on TypeLocs getAs behaves like a dyn_cast.
5) It could be a bug in this patch perhaps.
Let me know if you need any help!
Signed-off-by: Matheus Izvekov <mizvekov@gmail.com>
Differential Revision: https://reviews.llvm.org/D112374
This reverts commit 7c51f02eff because it
stills breaks the LLDB tests. This was re-landed without addressing the
issue or even agreement on how to address the issue. More details and
discussion in https://reviews.llvm.org/D112374.
Without this patch, clang will not wrap in an ElaboratedType node types written
without a keyword and nested name qualifier, which goes against the intent that
we should produce an AST which retains enough details to recover how things are
written.
The lack of this sugar is incompatible with the intent of the type printer
default policy, which is to print types as written, but to fall back and print
them fully qualified when they are desugared.
An ElaboratedTypeLoc without keyword / NNS uses no storage by itself, but still
requires pointer alignment due to pre-existing bug in the TypeLoc buffer
handling.
---
Troubleshooting list to deal with any breakage seen with this patch:
1) The most likely effect one would see by this patch is a change in how
a type is printed. The type printer will, by design and default,
print types as written. There are customization options there, but
not that many, and they mainly apply to how to print a type that we
somehow failed to track how it was written. This patch fixes a
problem where we failed to distinguish between a type
that was written without any elaborated-type qualifiers,
such as a 'struct'/'class' tags and name spacifiers such as 'std::',
and one that has been stripped of any 'metadata' that identifies such,
the so called canonical types.
Example:
```
namespace foo {
struct A {};
A a;
};
```
If one were to print the type of `foo::a`, prior to this patch, this
would result in `foo::A`. This is how the type printer would have,
by default, printed the canonical type of A as well.
As soon as you add any name qualifiers to A, the type printer would
suddenly start accurately printing the type as written. This patch
will make it print it accurately even when written without
qualifiers, so we will just print `A` for the initial example, as
the user did not really write that `foo::` namespace qualifier.
2) This patch could expose a bug in some AST matcher. Matching types
is harder to get right when there is sugar involved. For example,
if you want to match a type against being a pointer to some type A,
then you have to account for getting a type that is sugar for a
pointer to A, or being a pointer to sugar to A, or both! Usually
you would get the second part wrong, and this would work for a
very simple test where you don't use any name qualifiers, but
you would discover is broken when you do. The usual fix is to
either use the matcher which strips sugar, which is annoying
to use as for example if you match an N level pointer, you have
to put N+1 such matchers in there, beginning to end and between
all those levels. But in a lot of cases, if the property you want
to match is present in the canonical type, it's easier and faster
to just match on that... This goes with what is said in 1), if
you want to match against the name of a type, and you want
the name string to be something stable, perhaps matching on
the name of the canonical type is the better choice.
3) This patch could exposed a bug in how you get the source range of some
TypeLoc. For some reason, a lot of code is using getLocalSourceRange(),
which only looks at the given TypeLoc node. This patch introduces a new,
and more common TypeLoc node which contains no source locations on itself.
This is not an inovation here, and some other, more rare TypeLoc nodes could
also have this property, but if you use getLocalSourceRange on them, it's not
going to return any valid locations, because it doesn't have any. The right fix
here is to always use getSourceRange() or getBeginLoc/getEndLoc which will dive
into the inner TypeLoc to get the source range if it doesn't find it on the
top level one. You can use getLocalSourceRange if you are really into
micro-optimizations and you have some outside knowledge that the TypeLocs you are
dealing with will always include some source location.
4) Exposed a bug somewhere in the use of the normal clang type class API, where you
have some type, you want to see if that type is some particular kind, you try a
`dyn_cast` such as `dyn_cast<TypedefType>` and that fails because now you have an
ElaboratedType which has a TypeDefType inside of it, which is what you wanted to match.
Again, like 2), this would usually have been tested poorly with some simple tests with
no qualifications, and would have been broken had there been any other kind of type sugar,
be it an ElaboratedType or a TemplateSpecializationType or a SubstTemplateParmType.
The usual fix here is to use `getAs` instead of `dyn_cast`, which will look deeper
into the type. Or use `getAsAdjusted` when dealing with TypeLocs.
For some reason the API is inconsistent there and on TypeLocs getAs behaves like a dyn_cast.
5) It could be a bug in this patch perhaps.
Let me know if you need any help!
Signed-off-by: Matheus Izvekov <mizvekov@gmail.com>
Differential Revision: https://reviews.llvm.org/D112374
This reverts commit bdc6974f92 because it
breaks all the LLDB tests that import the std module.
import-std-module/array.TestArrayFromStdModule.py
import-std-module/deque-basic.TestDequeFromStdModule.py
import-std-module/deque-dbg-info-content.TestDbgInfoContentDequeFromStdModule.py
import-std-module/forward_list.TestForwardListFromStdModule.py
import-std-module/forward_list-dbg-info-content.TestDbgInfoContentForwardListFromStdModule.py
import-std-module/list.TestListFromStdModule.py
import-std-module/list-dbg-info-content.TestDbgInfoContentListFromStdModule.py
import-std-module/queue.TestQueueFromStdModule.py
import-std-module/stack.TestStackFromStdModule.py
import-std-module/vector.TestVectorFromStdModule.py
import-std-module/vector-bool.TestVectorBoolFromStdModule.py
import-std-module/vector-dbg-info-content.TestDbgInfoContentVectorFromStdModule.py
import-std-module/vector-of-vectors.TestVectorOfVectorsFromStdModule.py
https://green.lab.llvm.org/green/view/LLDB/job/lldb-cmake/45301/
Without this patch, clang will not wrap in an ElaboratedType node types written
without a keyword and nested name qualifier, which goes against the intent that
we should produce an AST which retains enough details to recover how things are
written.
The lack of this sugar is incompatible with the intent of the type printer
default policy, which is to print types as written, but to fall back and print
them fully qualified when they are desugared.
An ElaboratedTypeLoc without keyword / NNS uses no storage by itself, but still
requires pointer alignment due to pre-existing bug in the TypeLoc buffer
handling.
Signed-off-by: Matheus Izvekov <mizvekov@gmail.com>
Differential Revision: https://reviews.llvm.org/D112374
"Ascii" StringLiteral instances are actually narrow strings
that are UTF-8 encoded and do not have an encoding prefix.
(UTF8 StringLiteral are also UTF-8 encoded strings, but with
the u8 prefix.
To avoid possible confusion both with actuall ASCII strings,
and with future works extending the set of literal encodings
supported by clang, this rename StringLiteral::isAscii() to
isOrdinary(), matching C++ standard terminology.
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D128762
- Rename doc files to subdirs by module
- Update release notes and check list to use subdirs
- Update add_new_check.py to handle doc subdirs
Differential Revision: https://reviews.llvm.org/D126495
modernize-use-emplace only recommends going from a push_back to an
emplace_back, but does not provide a recommendation when emplace_back is
improperly used. This adds the functionality of warning the user when
an unecessary temporary is created while calling emplace_back or other "emplacy"
functions from the STL containers.
Reviewed By: kuhar, ivanmurashko
Differential Revision: https://reviews.llvm.org/D101471
C requires that enum values fit into an int. Scan the macro tokens
present in an initializing expression and reject macros that contain
tokens that have suffixes making them larger than int.
C forbids the comma operator in enum initializing expressions, so
optionally reject comma operator.
Differential Revision: https://reviews.llvm.org/D125622Fixes#55467
The end-user has no way of 'fixing' bugs in the system library anyway.
Let's suppress these as well.
Reviewed By: LegalizeAdulthood
Differential Revision: https://reviews.llvm.org/D125770
Unfortunately, we must restrict the checker to warn for deprecated headers
only if the header is included directly from a c++ source file.
For header files, we cannot know if the project has a C source file
that also directly/indirectly includes the offending header file
otherwise. Thus, it's better to be on the safe side and suppress those
reports.
One can opt-in the old behavior, emitting diagnostics into header files,
if one explicitly sets the WarnIntoHeaders=true, in which case nothing
will be changed.
Reviewed By: LegalizeAdulthood
Differential Revision: https://reviews.llvm.org/D125769
This partially reverts commit e8cae48702.
Changes since that commit:
- Use `SourceManager::isBeforeInTranslationUnit` instead of the fancy
decomposed decl logarithmic search.
- Add a test for including a system header containing a deprecated
include.
- Add `REQUIRES: system-linux` clause to the test.
Reviewed By: LegalizeAdulthood, whisperity
Differential Revision: https://reviews.llvm.org/D125209
Add a recursive descent parser to match macro expansion tokens against
fully formed valid expressions of integral literals. Partial
expressions will not be matched -- they can't be valid initializing
expressions for an enum.
Differential Revision: https://reviews.llvm.org/D124500Fixes#55055
The check should not report includes wrapped by `extern "C" { ... }` blocks,
such as:
```lang=C++
#ifdef __cplusplus
extern "C" {
#endif
#include "assert.h"
#ifdef __cplusplus
}
#endif
```
This pattern comes up sometimes in header files designed to be consumed
by both C and C++ source files.
The check now reports false reports when the header file is consumed by
a C++ translation unit.
In this change, I'm not emitting the reports immediately from the
`PPCallback`, rather aggregating them for further processing.
After all preprocessing is done, the matcher will be called on the
`TranslationUnitDecl`, ensuring that the check callback is called only
once.
Within that callback, I'm recursively visiting each decls, looking for
`LinkageSpecDecls` which represent the `extern "C"` specifier.
After this, I'm dropping all the reports coming from inside of it.
After the visitation is done, I'm emitting the reports I'm left with.
For performance reasons, I'm sorting the `IncludeMarkers` by their
corresponding locations.
This makes the scan `O(log(N)` when looking up the `IncludeMarkers`
affected by the given `extern "C"` block. For this, I'm using
`lower_bound()` and `upper_bound()`.
Reviewed By: whisperity
Differential Revision: https://reviews.llvm.org/D125209
There's many instances in clang tidy checks where owning strings are used when we already have a stable string from the options, so using a StringRef makes much more sense.
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D124341
If a macro is used in the expansion of another macro, that can cause
a compile error if the macro is replaced with an enum. Token-pasting is
an example where converting a macro defined as an integral constant can
cause code to no longer compile.
This change causes such macros to be skipped from the conversion
process in order to prevent fixits from creating code that no longer
compiles.
A subsequent enhancement will examine macro usage in more detail to
allow more cases to be handled without breaking code.
Differential Revision: https://reviews.llvm.org/D124316Fixes#54948
Modernize-macro-to-enum shouldn't try to convert macros to enums
when they are defined inside a declaration or definition, only
when the macros are defined at the top level. Since preprocessing
is disconnected from AST traversal, match nodes in the AST and then
invalidate source ranges spanning AST nodes before issuing diagnostics.
ClangTidyCheck::onEndOfTranslationUnit is called before
PPCallbacks::EndOfMainFile, so defer final diagnostics to the
PPCallbacks implementation.
Differential Revision: https://reviews.llvm.org/D124066Fixes#54883
When a macro is undef'ed or used in a preprocessor conditional
expression, we need to remember that macro should it later be
defined in the file to an integral value. We need to exclude
such macro names from being turned into an enum.
Maintain a blacklist of identifiers that we've seen in an
undef or conditional preprocessor directive. When the file is
done processing, remove all the blacklisted identifiers from
conversion to an enum.
Differential Revision: https://reviews.llvm.org/D123889Fixes#54842
Adds a flag to `ClangTidyContext` that is used to indicate to checks that fixes will only be applied one at a time.
This is to indicate to checks that each fix emitted should not depend on any other fixes emitted across the translation unit.
I've currently implemented the `IncludeInserter`, `LoopConvertCheck` and `PreferMemberInitializerCheck` to use these support these modes.
Reasoning behind this is in use cases like `clangd` it's only possible to apply one fix at a time.
For include inserter checks, the include is only added once for the first diagnostic that requires it, this will result in subsequent fixes not having the included needed.
A similar issue is seen in the `PreferMemberInitializerCheck` where the `:` will only be added for the first member that needs fixing.
Fixes emitted in `StandaloneDiagsMode` will likely result in malformed code if they are applied all together, conversely fixes currently emitted may result in malformed code if they are applied one at a time.
For this reason invoking `clang-tidy` from the binary will always with `StandaloneDiagsMode` disabled, However using it as a library its possible to select the mode you wish to use, `clangd` always selects `StandaloneDiagsMode`.
This is an example of the current behaviour failing
```lang=c++
struct Foo {
int A, B;
Foo(int D, int E) {
A = D;
B = E; // Fix Here
}
};
```
Incorrectly transformed to:
```lang=c++
struct Foo {
int A, B;
Foo(int D, int E), B(E) {
A = D;
// Fix Here
}
};
```
In `StandaloneDiagsMode`, it gets transformed to:
```lang=c++
struct Foo {
int A, B;
Foo(int D, int E) : B(E) {
A = D;
// Fix Here
}
};
```
Reviewed By: sammccall
Differential Revision: https://reviews.llvm.org/D97121
This patch changes type of the `File` parameter in `PPCallbacks::InclusionDirective()` from `const FileEntry *` to `Optional<FileEntryRef>`.
With the API change in place, this patch then removes some uses of the deprecated `FileEntry::getName()` (e.g. in `DependencyGraph.cpp` and `ModuleDependencyCollector.cpp`).
Reviewed By: dexonsmith, bnbarham
Differential Revision: https://reviews.llvm.org/D123574
When scanning a macro expansion to examine it as a candidate enum,
first strip off arbitrary matching parentheses from the outside in,
then examine what remains to see if it is Lit, +Lit, -Lit or ~Lit.
If not, reject it as a possible enum candidate.
Differential Revision: https://reviews.llvm.org/D123479Fixes#54843
When a "keyword" token like __restrict was present in a macro condition,
modernize-macro-to-enum would assert in non-release builds. However,
even for a "keyword" token, calling getIdentifierInfo()->getName() would
retrieve the text of the token, which is what we want. Our intention is
to scan names that appear in conditional expressions in potential enum
clusters and invalidate those clusters if they contain the name.
Also, guard against "raw identifiers" appearing as potential enums.
This shouldn't happen, but it doesn't hurt to generalize the code.
Differential Revision: https://reviews.llvm.org/D123349Fixes#54775
[buildbot issues fixed]
This check performs basic analysis of macros and replaces them
with an anonymous unscoped enum. Using an unscoped anonymous enum
ensures that everywhere the macro token was used previously, the
enumerator name may be safely used.
Potential macros for replacement must meet the following constraints:
- Macros must expand only to integral literal tokens. The unary
operators plus, minus and tilde are recognized to allow for positive,
negative and bitwise negated integers.
- Macros must be defined on sequential source file lines, or with
only comment lines in between macro definitions.
- Macros must all be defined in the same source file.
- Macros must not be defined within a conditional compilation block.
- Macros must not be defined adjacent to other preprocessor directives.
- Macros must not be used in preprocessor conditions
Each cluster of macros meeting the above constraints is presumed to
be a set of values suitable for replacement by an anonymous enum.
From there, a developer can give the anonymous enum a name and
continue refactoring to a scoped enum if desired. Comments on the
same line as a macro definition or between subsequent macro definitions
are preserved in the output. No formatting is assumed in the provided
replacements.
The check cppcoreguidelines-macro-to-enum is an alias for this check.
Fixes#27408
Differential Revision: https://reviews.llvm.org/D117522
This check performs basic analysis of macros and replaces them
with an anonymous unscoped enum. Using an unscoped anonymous enum
ensures that everywhere the macro token was used previously, the
enumerator name may be safely used.
Potential macros for replacement must meet the following constraints:
- Macros must expand only to integral literal tokens. The unary
operators plus, minus and tilde are recognized to allow for positive,
negative and bitwise negated integers.
- Macros must be defined on sequential source file lines, or with
only comment lines in between macro definitions.
- Macros must all be defined in the same source file.
- Macros must not be defined within a conditional compilation block.
- Macros must not be defined adjacent to other preprocessor directives.
- Macros must not be used in preprocessor conditions
Each cluster of macros meeting the above constraints is presumed to
be a set of values suitable for replacement by an anonymous enum.
From there, a developer can give the anonymous enum a name and
continue refactoring to a scoped enum if desired. Comments on the
same line as a macro definition or between subsequent macro definitions
are preserved in the output. No formatting is assumed in the provided
replacements.
The check cppcoreguidelines-macro-to-enum is an alias for this check.
Fixes#27408
Differential Revision: https://reviews.llvm.org/D117522
Implement P2128R6 in C++23 mode.
Unlike GCC's implementation, this doesn't try to recover when a user
meant to use a comma expression.
Because the syntax changes meaning in C++23, the patch is *NOT*
implemented as an extension. Instead, declaring an array with not
exactly 1 parameter is an error in older languages modes. There is an
off-by-default extension warning in C++23 mode.
Unlike the standard, we supports default arguments;
Ie, we assume, based on conversations in WG21, that the proposed
resolution to CWG2507 will be accepted.
We allow arrays OpenMP sections and C++23 multidimensional array to
coexist:
[a , b] multi dimensional array
[a : b] open mp section
[a, b: c] // error
The rest of the patch is relatively straight forward: we take care to
support an arbitrary number of arguments everywhere.
E.g. `Concept auto Func();`
The nameLoc for the constained auto type loc pointed to the concept name
loc, it should be the auto token loc. This patch fixes it, and remove
a relevant hack in clang-tidy check.
Reviewed By: sammccall
Differential Revision: https://reviews.llvm.org/D117009
The patch was reverted because it caused a crash during PCH build -- we
missed to update the RParenLoc in TreeTransform<Derived>::TransformAutoType.
This relands 55d96ac and 37ec65e with a test and fix.
Sometimes a macro invocation will look like an argument list
declaration. Improve the check to detect this situation and not
try to modify the macro invocation.
Thanks to Nathan James for the fix.
- Ignore implicit typedefs (e.g. compiler builtins)
- Improve lexing state machine to locate void argument tokens
- Add additional return_t() macro tests
- clang-format control in the test case file
- remove braces around single statements per LLVM style guide
Fixes#43791
Differential Revision: https://reviews.llvm.org/D116425
The check should not trigger on lvalue/rvalue overload pairs:
```
struct S {
S(const A& a) : a(a) {}
S(A&& a) : a(std::move(a)) {}
A a;
}
```
Differential Revision: https://reviews.llvm.org/D116535
We want to deal with non-default constructors that just happen to
contain constant initializers. There was already a negative test case,
it is now a positive one. We find and refactor this case:
struct PositiveNotDefaultInt {
PositiveNotDefaultInt(int) : i(7) {}
int i;
};
This reverts commit cc56c66f27.
Fixed a bad assertion, the target of a UsingShadowDecl must not have
*local* qualifiers, but it can be a typedef whose underlying type is qualified.
Fangrui Song