[NFC][libc++] Update clang-format style.

[Mordante]

Summary

Changes the style as requested by @ldionne in D103368.

[• Quuxplusone]

LGTM. (Although you know I think clang-format is useless for libc++ anyway.)

[Mordante]

Thanks. I still hope we can use clang-format after the LLVM-13 release. This should address our > > issue.

[ldionne]

libcxx/.clang-format

16

Does this mean it'll always be only indented by one space? What we need is to indent it to tabs, whatever the size of tabs are in a given file. Is there a way to achieve that?

[Mordante]

Sorry I forgot the submit my comment before.

libcxx/.clang-format

16

I assume you mean our standard indention of 2 spaces with "tabs". That would be achieved by removing this line, then it uses the default indention. I added this since you requested a one space indention D103368 and I've seen that indention used before in libc++.

[ldionne]

libcxx/.clang-format

16

Sorry if we misunderstood each other -- what I want is for #ifs to be indented consistently with the surrounding indentation, period. So if the surrounding indentation uses 4 tabs, nested preprocessor directives should look like:

#if CONDITION
#   define FOO
    ^ 5th column, i.e. indentation consists of 1x'#' and 3x' '
#endif

Similarly, if surrounding indentation uses 2 spaces, then it should look like:

#if CONDITION
# define FOO
  ^ 3rd column, i.e. indentation consists of 1x'#' and 1x' '
#endif

Does that make sense?

[ldionne]

libcxx/.clang-format

16

So if the surrounding indentation uses 4 tabs 4 spaces

(just to clarify what I meant)

[• Quuxplusone]

libcxx/.clang-format

16

FWIW, bleagh. I've never seen libc++ do

void f() {
#if SOMETHING
    int x;
#    if SOMETHINGELSE
    int y;
#    endif // SOMETHINGELSE
#endif // SOMETHING
}

nor do I think that's a good style. I think that in running code libc++'s style is generally "no indents at all":

void f() {
#if SOMETHING
    int x;
#if SOMETHINGELSE
    int y;
#endif // SOMETHINGELSE
#endif // SOMETHING
}

and in preprocessor code it's generally "one space":

#if SOMETHING
# define X y
# if SOMETHINGELSE
#  define Y z
# endif // SOMETHINGELSE
#endif // SOMETHING

Of course as usual clang-format can't handle that complicated of a rule (it has no notion of "preprocessor code" versus "normal code"). Ultimately we just have to just pick something for the .clang-format file and advise people to ignore it if it seems to be doing the wrong thing.

[ldionne]

libcxx/.clang-format

16

My comment only referred to "preprocessor code", not "normal code". Indeed, we don't do

void f() {
#if SOMETHING
    int x;
#    if SOMETHINGELSE
    int y;
#    endif // SOMETHINGELSE
#endif // SOMETHING
}

However, what I want to avoid at all costs is unreadable crazy stuff like this:

#if defined(_LIBCPP_HAS_THREAD_API_PTHREAD)
#if defined(__ANDROID__) && __ANDROID_API__ >= 30
#define _LIBCPP_HAS_COND_CLOCKWAIT
#elif defined(_LIBCPP_GLIBC_PREREQ)
#if _LIBCPP_GLIBC_PREREQ(2, 30)
#define _LIBCPP_HAS_COND_CLOCKWAIT
#endif
#endif
#endif

If anyone wrote normal code with ifs without indentation like that, we'd tell them it's unreadable. The same applies to the preprocessor.

To go back to this review, I think what we want is

# libc++'s preferred indentions of preprocessor statements.
IndentPPDirectives: AfterHash

That's it. We don't specify the tab size cause that depends on what file you're in.

[Mordante]

Remove PPIndentWidth: 1

libcxx/.clang-format

 BasedOnStyle: LLVM
 
 ---
 Language: Cpp
 Standard: Cpp03
 
 AlwaysBreakTemplateDeclarations: true
 PointerAlignment: Left
 
 # Disable formatting options which may break tests.
 SortIncludes: false
 ReflowComments: false
 
+# libc++'s preferred indentions of preprocessor statements.
+IndentPPDirectives: AfterHash
+
 # libc++ has some long names so we need more than the 80 column limit imposed by LLVM style, for sensible formatting
 ColumnLimit: 120
 ---