Avoid cast alignment warning in cache string view

The cache allocates strings as

    uint16_t size;
    char content[];
    char zero;

Aligned to the uint16_t. When doing the casting, this causes a
warning on some architectures that cannot do unaligned loads, such
as armhf.

Use __builtin_assume_aligned() to explictly say that the pointer
is aligned to 16 bits. This is a bit of a backhanded approach,
as the warning seems to be actually avoided by the function
returning a void* rather than the assumed alignment, but this
is very much self-documenting.

1 files changed, 1 insertions, 1 deletions

diff --git a/apt-pkg/pkgcache.h b/apt-pkg/pkgcache.h
index b832106ed..7a9db3d20 100644
--- a/apt-pkg/pkgcache.h
+++ b/apt-pkg/pkgcache.h
@@ -258,7 +258,7 @@ class APT_PUBLIC pkgCache								/*{{{*/
    std::string_view ViewString(map_stringitem_t idx) const
    {
       char *name = StrP + idx;
-      size_t len = *reinterpret_cast<const uint16_t*>(name - sizeof(uint16_t));
+      size_t len = *reinterpret_cast<const uint16_t *>(__builtin_assume_aligned(name - sizeof(uint16_t), sizeof(uint16_t)));
       return {name, len};
    }