vedgy added inline comments.
================
Comment at: clang/include/clang-c/Index.h:329
+ * CXIndexOptions Opts = { sizeof(CXIndexOptions),
+ * clang_getDefaultGlobalOptions() };
+ * \endcode
----------------
aaron.ballman wrote:
> vedgy wrote:
> > When I almost finished the requested changes, I remembered that the return
> > value of `clang_getDefaultGlobalOptions()` depends on environment
> > variables, and thus `0` is not necessarily the default. Adjusted the
> > changes and updated this revision.
> >
> > Does the extra requirement to non-zero initialize this second member sway
> > your opinion on the usefulness of the helper function `inline
> > CXIndexOptions clang_getDefaultIndexOptions()`? Note that there may be same
> > (environment) or other important reasons why future new options couldn't be
> > zeroes by default.
> Thinking out loud a bit... (potentially bad idea incoming)
>
> What if we dropped `clang_getDefaultGlobalOptions()` and instead made a
> change to `CXGlobalOptFlags`:
> ```
> typedef enum {
> /**
> * Used to indicate that the default CXIndex options are used. By default,
> no
> * global options will be used. However, environment variables may change
> which
> * global options are in effect at runtime.
> */
> CXGlobalOpt_Default = 0x0,
>
> /**
> * Used to indicate that threads that libclang creates for indexing
> * purposes should use background priority.
> *
> * Affects #clang_indexSourceFile, #clang_indexTranslationUnit,
> * #clang_parseTranslationUnit, #clang_saveTranslationUnit.
> */
> CXGlobalOpt_ThreadBackgroundPriorityForIndexing = 0x1,
>
> /**
> * Used to indicate that threads that libclang creates for editing
> * purposes should use background priority.
> *
> * Affects #clang_reparseTranslationUnit, #clang_codeCompleteAt,
> * #clang_annotateTokens
> */
> CXGlobalOpt_ThreadBackgroundPriorityForEditing = 0x2,
>
> /**
> * Used to indicate that all threads that libclang creates should use
> * background priority.
> */
> CXGlobalOpt_ThreadBackgroundPriorityForAll =
> CXGlobalOpt_ThreadBackgroundPriorityForIndexing |
> CXGlobalOpt_ThreadBackgroundPriorityForEditing,
>
> /**
> * Used to indicate that no global options should be used, even
> * in the presence of environment variables.
> */
> CXGlobalOpt_None = 0xFFFFFFFF
> } CXGlobalOptFlags;
> ```
> so that when the user passes `0` they get the previous behavior.
>
> `clang_CXIndex_setGlobalOptions()` would remain deprecated.
> `clang_CXIndex_getGlobalOptions()` would be interesting though -- would it
> return `CXGlobalOpt_None` or `CXGlobalOpt_Default` in the event the index was
> created without any global options? Hmmm.
>
> Err, actually, I suppose this won't work too well because then code silently
> changes behavior if it does
> `clang_CXIndex_setGlobalOptions(CXGlobalOpt_None);` because that would change
> from "do what the environment says" to "ignore the environment". But I have
> to wonder whether anyone actually *does* that or not... my intuition is that
> folks would not call `clang_CXIndex_setGlobalOptions()` at all unless they
> were setting an option to a non-none value. We could rename
> `CXGlobalOpt_None` to `CXGlobalOpt_Nothing` (or something along those lines)
> to force a compilation error, but that's a bit of a nuclear option for what's
> supposed to be a stable API.
>
> So I'm on the fence, I guess. I'd still prefer for zero to give sensible
> defaults and I don't think there's enough use of the global options +
> environment variables to matter. But I also don't like silently breaking
> code, so my idea above may be a nonstarter.
>
> I suppose another possible idea is: deprecate the notion of global options
> enum and setter/getter entirely, add two new fields to `CXIndexOptions`:
> ```
> typedef enum {
> CXChoice_Default = 0,
> CXChoice_Enabled = 1,
> CXChoice_Disabled = 2
> } CXChoice;
>
> ...
> unsigned ThreadPriorityBackgroundForIndexing;
> unsigned ThreadPriorityBackgroundForEditing;
> ...
> ```
> so that `0` gives the correct default behavior based on environment variable.
> There would be no global setter or getter for this information (and we'd
> eventually remove `clang_CXIndex_[gs]etGlobalOptions()`).
> I suppose this won't work too well because then code silently changes
> behavior if it does `clang_CXIndex_setGlobalOptions(CXGlobalOpt_None);`
> because that would change from "do what the environment says" to "ignore the
> environment".
No, the current consequence of such a call already is to ignore the
environment. What would change is the consequence of calling
`clang_CXIndex_setGlobalOptions(0);` - from "ignore the environment" to "do
what the environment says".
> But I have to wonder whether anyone actually *does* that or not... my
> intuition is that folks would not call `clang_CXIndex_setGlobalOptions()` at
> all unless they were setting an option to a non-none value.
I agree. Possible unlikely reasons to call `clang_CXIndex_setGlobalOptions(0)`
are:
1) in case the environment variables are set for some other program;
2) in case setting the environment variables had been useful in the past but
not in the latest and greatest version of an IDE;
3) if background priority is never useful for an IDE.
> I suppose another possible idea is: deprecate the notion of global options
> enum and setter/getter entirely, add two new fields to CXIndexOptions
This appears to be a great idea to me. The notion of `CXGlobalOptFlags`
somewhat conflicts with the new `CXIndexOptions` struct, in which two other
boolean options are represented by bit-fields.
I think we can forbid from the start calling
`clang_CXIndex_[gs]etGlobalOptions()` if the index is created via the new
function `clang_createIndexWithOptions`.
If 3-state environment variables (unspecified/on/off) are introduced in the
future, `CXChoice` could be extended with `CXChoice_FromEnvironmentOrEnabled =
3` to indicate that if the environment variable is present, its value should be
respected, otherwise the thread priority should be enabled.
`CXChoice` cannot possibly have many valid values. So how about:
```
unsigned char ThreadPriorityBackgroundForIndexing;
unsigned char ThreadPriorityBackgroundForEditing;
```
Then `size_t Size` could become `unsigned Size` and all non-pointer options
would fit into 8 bytes on x86_64.
Did you reorder the words in the variable names intentionally?
`CXGlobalOpt_ThreadBackgroundPriorityForIndexing` =>
`ThreadPriorityBackgroundForIndexing`
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D143418/new/
https://reviews.llvm.org/D143418
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