The recent change to represent language and target attribute tables using
vec.h's array_slice template class triggers an issue/bug in older g++
compilers, specifically the g++ 4.8.5 system compiler of older RedHat
distributions.  This exhibits as the following compilation errors during
bootstrap:

../../gcc/gcc/c/c-lang.cc:55:2661: error: could not convert '(const
scoped_attribute_specs* const*)(& c_objc_attribute_table)' from 'const
scoped_attribute_specs* const*' to 'array_slice<const
scoped_attribute_specs* const>'
 struct lang_hooks lang_hooks = LANG_HOOKS_INITIALIZER;

../../gcc/gcc/c/c-decl.cc:4657:1: error: could not convert '(const
attribute_spec*)(& std_attributes)' from 'const attribute_spec*' to
'array_slice<const attribute_spec>'

Here the issue is with constructors of the from:

static const int table[] = { 1, 2, 3 };
array_slice<int> t = table;

Perhaps there's a fix possible in vec.h (an additional constructor?), but
the patch below fixes this issue by using one of array_slice's constructors
(that takes a size) explicitly, rather than rely on template resolution.
In the example above this looks like:

array_slice<int> t (table, 3);

or equivalently

array_slice<int> t = array_slice<int>(table, 3);

or equivalently

array_slice<int> t = array_slice<int>(table, ARRAY_SIZE (table));


This patch has been tested on x86_64-pc-linux-gnu with make bootstrap,
where these changes allow the bootstrap to complete.  Ok for mainline?
This fix might not by ideal, but it both draws attention to the problem
and restores bootstrap whilst better approaches are investigated.  For
example, an ARRAY_SLICE(table) macro might be appropriate if there isn't
an easy/portable template resolution solution.  Thoughts?


2023-12-03  Roger Sayle  <roger@nextmovesoftware.com>

gcc/c-family/ChangeLog
        * c-attribs.cc (c_common_gnu_attribute_table): Use an explicit
        array_slice constructor with an explicit size argument.
        (c_common_format_attribute_table): Likewise.

gcc/c/ChangeLog
        * c-decl.cc (std_attribute_table): Use an explicit
        array_slice constructor with an explicit size argument.
        * c-objc-common.h (LANG_HOOKS_ATTRIBUTE_TABLE): Likewise.

gcc/ChangeLog
        * config/i386/i386-options.cc (ix86_gnu_attribute_table): Use an
        explicit array_slice constructor with an explicit size argument.
        * config/i386/i386.cc (TARGET_ATTRIBUTE_TABLE): Likewise.

gcc/cp/ChangeLog
        * cp-objcp-common.h (LANG_HOOKS_ATTRIBUTE_TABLE): Use an
        explicit array_slice constructor with an explicit size argument.
        * tree.cc (cxx_gnu_attribute_table): Likewise.
        (std_attribute_table): Likewise.

gcc/lto/ChangeLog
        * lto-lang.cc (lto_gnu_attribute_table): Use an explicit
        array_slice constructor with an explicit size argument.
        (lto_format_attribute_table): Likewise.
        (LANG_HOOKS_ATTRIBUTE_TABLE): Likewise.


Thanks in advance,
Roger
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