[llvm] r185831 - Use Clang's __has_* macros in Compiler.h to test for features

David Dean david_dean at apple.com
Mon Jul 8 10:00:07 PDT 2013 

On 8 Jul 2013, at 9:39 AM, Reid Kleckner <rnk at google.com> wrote:

> Prospective fix in r185833.
> 
> I can't reproduce the bot problem locally when building clang with a ~month-old clang.  Is there anything special about that bot?  Is it building with a clang from XCode, maybe?

This particular bot isn't bootstrapping and is doing incremental builds so that we get fast turnaround. It is using the clang in the system which should match a recent Xcode release.

> I also didn't receive any mail or IRC notifications about the failure.  Is that a known issue?

Michael Gottesman disabled the irc notifications and email because of some bugs. I'll pester him about them later today.


> On Mon, Jul 8, 2013 at 12:08 PM, David Dean <david_dean at apple.com> wrote:
> This commit has broken some of the buildbots:
> 
> http://lab.llvm.org:8013/builders/clang-x86_64-darwin11-nobootstrap-RAincremental/builds/4079
> 
> /Users/buildslave/zorg/buildbot/smooshlab/slave-0.8/build.clang-x86_64-darwin11-nobootstrap-RAincremental/llvm/include/llvm/Support/Compiler.h:204:5: error: builtin feature check macro requires a parenthesized identifier
> #if __has_attribute(const) || defined(__GNUC__)
>     ^
> /Users/buildslave/zorg/buildbot/smooshlab/slave-0.8/build.clang-x86_64-darwin11-nobootstrap-RAincremental/llvm/include/llvm/Support/Compiler.h:204:26: error: expected end of line in preprocessor expression
> 
> Please fix or revert as soon as you can.
> 
> On 8 Jul 2013, at 8:31 AM, Reid Kleckner <reid at kleckner.net> wrote:
> 
> > Author: rnk
> > Date: Mon Jul  8 10:31:29 2013
> > New Revision: 185831
> >
> > URL: http://llvm.org/viewvc/llvm-project?rev=185831&view=rev
> > Log:
> > Use Clang's __has_* macros in Compiler.h to test for features
> >
> > When targetting Windows, clang does not define __GNUC__, and as a result
> > we don't use our attributes with it.  This leads to warnings about
> > unused functions that are already annotated with LLVM_ATTRIBUTE_UNUSED.
> > Rather than testing for __clang__, we can use its __has_attribute and
> > __has_builtin macros directlty.
> >
> > While I'm here, conditionally define and use __GNUC_PREREQ for gcc
> > version checks.  Spelling the check out with three comparisons is
> > verbose and error prone.
> >
> > Reviewers: aaron.ballman
> >
> > Differential Revision: http://llvm-reviews.chandlerc.com/D1080
> >
> > Modified:
> >    llvm/trunk/include/llvm/Support/Compiler.h
> >
> > Modified: llvm/trunk/include/llvm/Support/Compiler.h
> > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/Compiler.h?rev=185831&r1=185830&r2=185831&view=diff
> > ==============================================================================
> > --- llvm/trunk/include/llvm/Support/Compiler.h (original)
> > +++ llvm/trunk/include/llvm/Support/Compiler.h Mon Jul  8 10:31:29 2013
> > @@ -21,6 +21,25 @@
> > # define __has_feature(x) 0
> > #endif
> >
> > +#ifndef __has_attribute
> > +# define __has_attribute(x) 0
> > +#endif
> > +
> > +#ifndef __has_builtin
> > +# define __has_builtin(x) 0
> > +#endif
> > +
> > +/// \macro __GNUC_PREREQ
> > +/// \brief Defines __GNUC_PREREQ if glibc's features.h isn't available.
> > +#ifndef __GNUC_PREREQ
> > +# if defined(__GNUC__) && defined(__GNUC_MINOR__)
> > +#  define __GNUC_PREREQ(maj, min) \
> > +    ((__GNUC__ << 16) + __GNUC_MINOR__ >= ((maj) << 16) + (min))
> > +# else
> > +#  define __GNUC_PREREQ(maj, min) 0
> > +# endif
> > +#endif
> > +
> > /// \brief Does the compiler support r-value references?
> > /// This implies that <utility> provides the one-argument std::move;  it
> > /// does not imply the existence of any other C++ library features.
> > @@ -146,13 +165,15 @@
> > /// into a shared library, then the class should be private to the library and
> > /// not accessible from outside it.  Can also be used to mark variables and
> > /// functions, making them private to any shared library they are linked into.
> > -#if (__GNUC__ >= 4) && !defined(__MINGW32__) && !defined(__CYGWIN__)
> > +/// On PE/COFF targets, library visibility is the default, so this isn't needed.
> > +#if (__has_attribute(visibility) || __GNUC_PREREQ(4, 0)) &&                    \
> > +    !defined(__MINGW32__) && !defined(__CYGWIN__) && !defined(LLVM_ON_WIN32)
> > #define LLVM_LIBRARY_VISIBILITY __attribute__ ((visibility("hidden")))
> > #else
> > #define LLVM_LIBRARY_VISIBILITY
> > #endif
> >
> > -#if (__GNUC__ >= 4 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 1))
> > +#if __has_attribute(used) || __GNUC_PREREQ(3, 1)
> > #define LLVM_ATTRIBUTE_USED __attribute__((__used__))
> > #else
> > #define LLVM_ATTRIBUTE_USED
> > @@ -166,31 +187,35 @@
> > // more portable solution:
> > //   (void)unused_var_name;
> > // Prefer cast-to-void wherever it is sufficient.
> > -#if (__GNUC__ >= 4 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 1))
> > +#if __has_attribute(unused) || __GNUC_PREREQ(3, 1)
> > #define LLVM_ATTRIBUTE_UNUSED __attribute__((__unused__))
> > #else
> > #define LLVM_ATTRIBUTE_UNUSED
> > #endif
> >
> > -#if (__GNUC__ >= 4) && !defined(__MINGW32__) && !defined(__CYGWIN__)
> > +// FIXME: Provide this for PE/COFF targets.
> > +#if (__has_attribute(weak) || __GNUC_PREREQ(4, 0)) &&                          \
> > +    (!defined(__MINGW32__) && !defined(__CYGWIN__) && !defined(LLVM_ON_WIN32))
> > #define LLVM_ATTRIBUTE_WEAK __attribute__((__weak__))
> > #else
> > #define LLVM_ATTRIBUTE_WEAK
> > #endif
> >
> > -#ifdef __GNUC__ // aka 'CONST' but following LLVM Conventions.
> > +#if __has_attribute(const) || defined(__GNUC__)
> > +// aka 'CONST' but following LLVM Conventions.
> > #define LLVM_READNONE __attribute__((__const__))
> > #else
> > #define LLVM_READNONE
> > #endif
> >
> > -#ifdef __GNUC__  // aka 'PURE' but following LLVM Conventions.
> > +#if __has_attribute(pure) || defined(__GNUC__)
> > +// aka 'PURE' but following LLVM Conventions.
> > #define LLVM_READONLY __attribute__((__pure__))
> > #else
> > #define LLVM_READONLY
> > #endif
> >
> > -#if (__GNUC__ >= 4)
> > +#if __has_builtin(__builtin_expect) || __GNUC_PREREQ(4, 0)
> > #define LLVM_LIKELY(EXPR) __builtin_expect((bool)(EXPR), true)
> > #define LLVM_UNLIKELY(EXPR) __builtin_expect((bool)(EXPR), false)
> > #else
> > @@ -213,7 +238,7 @@
> >
> > /// LLVM_ATTRIBUTE_NOINLINE - On compilers where we have a directive to do so,
> > /// mark a method "not for inlining".
> > -#if (__GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4))
> > +#if __has_attribute(noinline) || __GNUC_PREREQ(3, 4)
> > #define LLVM_ATTRIBUTE_NOINLINE __attribute__((noinline))
> > #elif defined(_MSC_VER)
> > #define LLVM_ATTRIBUTE_NOINLINE __declspec(noinline)
> > @@ -225,7 +250,7 @@
> > /// so, mark a method "always inline" because it is performance sensitive. GCC
> > /// 3.4 supported this but is buggy in various cases and produces unimplemented
> > /// errors, just use it in GCC 4.0 and later.
> > -#if __GNUC__ > 3
> > +#if __has_attribute(always_inline) || __GNUC_PREREQ(4, 0)
> > #define LLVM_ATTRIBUTE_ALWAYS_INLINE inline __attribute__((always_inline))
> > #elif defined(_MSC_VER)
> > #define LLVM_ATTRIBUTE_ALWAYS_INLINE __forceinline
> > @@ -267,8 +292,7 @@
> > /// LLVM_BUILTIN_UNREACHABLE - On compilers which support it, expands
> > /// to an expression which states that it is undefined behavior for the
> > /// compiler to reach this point.  Otherwise is not defined.
> > -#if defined(__clang__) || (__GNUC__ > 4) \
> > - || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5)
> > +#if __has_builtin(__builtin_unreachable) || __GNUC_PREREQ(4, 5)
> > # define LLVM_BUILTIN_UNREACHABLE __builtin_unreachable()
> > #elif defined(_MSC_VER)
> > # define LLVM_BUILTIN_UNREACHABLE __assume(false)
> > @@ -276,8 +300,7 @@
> >
> > /// LLVM_BUILTIN_TRAP - On compilers which support it, expands to an expression
> > /// which causes the program to exit abnormally.
> > -#if defined(__clang__) || (__GNUC__ > 4) \
> > - || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
> > +#if __has_builtin(__builtin_trap) || __GNUC_PREREQ(4, 3)
> > # define LLVM_BUILTIN_TRAP __builtin_trap()
> > #else
> > # define LLVM_BUILTIN_TRAP *(volatile int*)0x11 = 0
> > @@ -285,11 +308,10 @@
> >
> > /// \macro LLVM_ASSUME_ALIGNED
> > /// \brief Returns a pointer with an assumed alignment.
> > -#if !defined(__clang__) && ((__GNUC__ > 4) \
> > - || (__GNUC__ == 4 && __GNUC_MINOR__ >= 7))
> > -// FIXME: Enable on clang when it supports it.
> > +#if __has_builtin(__builtin_assume_aligned) && __GNUC_PREREQ(4, 7)
> > # define LLVM_ASSUME_ALIGNED(p, a) __builtin_assume_aligned(p, a)
> > #elif defined(LLVM_BUILTIN_UNREACHABLE)
> > +// As of today, clang does not support __builtin_assume_aligned.
> > # define LLVM_ASSUME_ALIGNED(p, a) \
> >            (((uintptr_t(p) % (a)) == 0) ? (p) : (LLVM_BUILTIN_UNREACHABLE, (p)))
> > #else
> >
> >
> > _______________________________________________
> > llvm-commits mailing list
> > llvm-commits at cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
> 
> -David
> 
> 
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-David

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