This PR is 2nd part of
[P1857R3](https://github.com/llvm/llvm-project/pull/107168)
implementation, and mainly implement the restriction `A module directive
may only appear as the first preprocessing tokens in a file (excluding
the global module fragment.)`:
[cpp.pre](https://eel.is/c++draft/cpp.pre):
```
module-file:
pp-global-module-fragment[opt] pp-module group[opt] pp-private-module-fragment[opt]
```
We also refine tests use `split-file` instead of conditional macro.
Signed-off-by: yronglin <yronglin777@gmail.com>
Close https://github.com/llvm/llvm-project/issues/90154
This patch is also an optimization to the lookup process to utilize the
information provided by `export` keyword.
Previously, in the lookup process, the `export` keyword only takes part
in the check part, it doesn't get involved in the lookup process. That
said, previously, in a name lookup for 'name', we would load all of
declarations with the name 'name' and check if these declarations are
valid or not. It works well. But it is inefficient since it may load
declarations that may not be wanted.
Note that this patch actually did a trick in the lookup process instead
of bring module information to DeclarationName or considering module
information when deciding if two declarations are the same. So it may
not be a surprise to me if there are missing cases. But it is not a
regression. It should be already the case. Issue reports are welcomed.
In this patch, I tried to split the big lookup table into a lookup table
as before and a module local lookup table, which takes a combination of
the ID of the DeclContext and hash value of the primary module name as
the key. And refactored `DeclContext::lookup()` method to take the
module information. So that a lookup in a DeclContext won't load
declarations that are local to **other** modules.
And also I think it is already beneficial to split the big lookup table
since it may reduce the conflicts during lookups in the hash table.
BTW, this patch introduced a **regression** for a reachability rule in
C++20 but it was false-negative. See
'clang/test/CXX/module/module.interface/p7.cpp' for details.
This patch is not expected to introduce any other
regressions for non-c++20-modules users since the module local lookup
table should be empty for them.
Close https://github.com/llvm/llvm-project/issues/90154
This patch is also an optimization to the lookup process to utilize the
information provided by `export` keyword.
Previously, in the lookup process, the `export` keyword only takes part
in the check part, it doesn't get involved in the lookup process. That
said, previously, in a name lookup for 'name', we would load all of
declarations with the name 'name' and check if these declarations are
valid or not. It works well. But it is inefficient since it may load
declarations that may not be wanted.
Note that this patch actually did a trick in the lookup process instead
of bring module information to DeclarationName or considering module
information when deciding if two declarations are the same. So it may
not be a surprise to me if there are missing cases. But it is not a
regression. It should be already the case. Issue reports are welcomed.
In this patch, I tried to split the big lookup table into a lookup table
as before and a module local lookup table, which takes a combination of
the ID of the DeclContext and hash value of the primary module name as
the key. And refactored `DeclContext::lookup()` method to take the
module information. So that a lookup in a DeclContext won't load
declarations that are local to **other** modules.
And also I think it is already beneficial to split the big lookup table
since it may reduce the conflicts during lookups in the hash table.
BTW, this patch introduced a **regression** for a reachability rule in
C++20 but it was false-negative. See
'clang/test/CXX/module/module.interface/p7.cpp' for details.
This patch is not expected to introduce any other
regressions for non-c++20-modules users since the module local lookup
table should be empty for them.
---
On the API side, this patch unfortunately add a maybe-confusing argument
`Module *NamedModule` to
`ExternalASTSource::FindExternalVisibleDeclsByName()`. People may think
we can get the information from the first argument `const DeclContext
*DC`. But sadly there are declarations (e.g., namespace) can appear in
multiple different modules as a single declaration. So we have to add
additional information to indicate this.
Close https://github.com/llvm/llvm-project/issues/60824
The form -fmodule-file=<path-to-BMI> will load modules eagerly and the
form -fmodule-file=<module-name>=<path-to-BMI> will load modules lazily.
The inconsistency adds many additional burdens to the implementations.
And the inconsistency looks not helpful and necessary neither. So I want
to deprecate the form -fmodule-file=<path-to-BMI> for named modules.
This is pretty helpful for us (the developers).
Does this change make any regression from the perspective of the users?
To be honest, yes. But I think such regression is acceptable. Here is
the example:
```
// M.cppm
export module M;
export int m = 5;
// N.cpp
// import M; // woops, we forgot to import M.
int n = m;
```
In the original version, the compiler can diagnose the users to import
`M` since the compiler have already imported M. But in the later style,
the compiler can only say "unknown identifier `m`".
But I think such regression doesn't make a deal since it only works if
the user put `-fmodule-file=M.pcm` in the command line. But how can the
user put `-fmodule-file=M.pcm` in the command line without `import M;`?
Especially currently such options are generated by build systems. And
the build systems will only generate the command line from the source
file.
So I think this change is pretty pretty helpful for developers and
almost innocent for users and we should accept this one.
I'll add the release notes and edit the document after we land this.
Differential Revision: https://reviews.llvm.org/D144707
Fix a few bugs where we would fail to properly determine header to
module correspondence when determining whether to suggest a #include or
import, and suggest a #include more often in language modes where there
is no import syntax. Generally, if the target is in a header with
include guards or #pragma once, we should suggest either #including or
importing that header, and not importing a module that happens to
textually include it.
In passing, improve the notes we attach to the corresponding
diagnostics: calling an entity that we couldn't see "previous" is
confusing.
global module fragment.
We know that the declaration in question should have been introduced by
a '#include', so try to figure out which one and suggest it. Don't
suggest importing the global module fragment itself!
llvm-svn: 358631
