Update asserts in mojo about int64_t's alignment

The purpose of these asserts is to check that the options structs are aligned
sufficiently that an int64_t (or similar) could be added to them. The asserts
were added in https://codereview.chromium.org/295383012

However, the alignment of int64_t on 32-bit x86 is actually 4 bytes, not 8. So
how did this ever work? Before Clang r345419, the alignof() operator (which is what
MOJO_ALIGNOF maps to) would return the *preferred alignment* of a type, not
the *ABI alignment*. That's not what the C and C++ standards specify, so the
bug was fixed and the asserts started firing. (See also
https://llvm.org/pr26547)

To fix the build, change the asserts to check that int64_t requires 8 bytes
alignment *or less*.

Bug: 900406
Bug: 119634736
Test: make checkbuild
Change-Id: Icf80cea80ac31082423faab8c192420d0b98d515
Reviewed-on: https://chromium-review.googlesource.com/c/1318971
Commit-Queue: Ken Rockot <rockot@google.com>
Reviewed-by: Ken Rockot <rockot@google.com>
Cr-Commit-Position: refs/heads/master@{#605699}

(Reconstructed from 9525530ea4ee4d70b55b5b376ad96ecdd587bd39)

1 files changed, 1 insertions, 1 deletions

diff --git a/mojo/public/c/system/buffer.h b/mojo/public/c/system/buffer.h
index 2cc54270ad..83b198b2a8 100644
--- a/mojo/public/c/system/buffer.h
+++ b/mojo/public/c/system/buffer.h
@@ -30,7 +30,7 @@ struct MOJO_ALIGNAS(8) MojoCreateSharedBufferOptions {
   // See |MojoCreateSharedBufferFlags|.
   MojoCreateSharedBufferFlags flags;
 };
-MOJO_STATIC_ASSERT(MOJO_ALIGNOF(int64_t) == 8, "int64_t has weird alignment");
+MOJO_STATIC_ASSERT(MOJO_ALIGNOF(int64_t) <= 8, "int64_t has weird alignment");
 MOJO_STATIC_ASSERT(sizeof(MojoCreateSharedBufferOptions) == 8,
                    "MojoCreateSharedBufferOptions has wrong size");