[PATCH] Restore build with GCC 4.8 to GCC 5 (was Re: [PATCH] Workaround array_slice constructor portability issues (with older g++).)

[Richard Sandiford <richard.sandiford@arm.com>]

Richard Sandiford <richard.sandiford@arm.com> writes:
> "Roger Sayle" <roger@nextmovesoftware.com> writes:
>> 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;
>
> It's array_slice<const int> rather than array_slice<int>.  The above
> would be invalid even with functioning compilers.
>
>> 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));
>
> Taking c-decl.cc as an arbitrary example, it seems to be enough to change:
>
> const scoped_attribute_specs std_attribute_table =
> {
>   nullptr, std_attributes
> };
>
> to:
>
> const scoped_attribute_specs std_attribute_table =
> {
>   nullptr, { std_attributes }
> };
>
> which seems less ugly than the explicit constructors.
>
> But if we're going to do this, we should do it across the board,
> not just for x86.

Here's an attempt to do that.  Tested so far by building
aarch64-linux-gnu (which has target attributes) and frv-elf
(which doesn't) with GCC 4.8.

OK if further testing passes?

Richard

---

GCC 5 and earlier applied array-to-pointer decay too early,
which affected the new attribute namespace code.  A reduced
example of the construct that the attribute code uses is:

    struct S { template<__SIZE_TYPE__ N> S(int (&)[N]); };
    struct T { int a; S b; };
    int a[] = { 1 };
    T t = { 1, a };

This was fixed by f85e1317f8ea933f5c615680353bd646f480f7d3
(PR 16333 et al).

This patch tries to add a minimally-invasive workaround.

gcc/ada/
	* gcc-interface/utils.cc (gnat_internal_attribute_table): Add extra
	braces to work around PR 16333 in older compilers.

gcc/
	* attribs.cc (handle_ignored_attributes_option): Add extra
	braces to work around PR 16333 in older compilers.
	* config/arm/arm.cc (arm_gnu_attribute_table): Likewise.
	* config/i386/i386-options.cc (ix86_gnu_attribute_table): Likewise.
	* config/ia64/ia64.cc (ia64_gnu_attribute_table): Likewise.
	* config/rs6000/rs6000.cc (rs6000_gnu_attribute_table): Likewise.
	* target-def.h (TARGET_GNU_ATTRIBUTES): Likewise.
	* genhooks.cc (emit_init_macros): Likewise, when emitting the
	instantiation of TARGET_ATTRIBUTE_TABLE.
	* langhooks-def.h (LANG_HOOKS_INITIALIZER): Likewise, when
	instantiating LANG_HOOKS_ATTRIBUTE_TABLE.
	(LANG_HOOKS_ATTRIBUTE_TABLE): Define to be empty by default.
	* target.def (attribute_table): Likewise.

gcc/c-family/
	* c-attribs.cc (c_common_gnu_attribute_table): Add extra
	braces to work around PR 16333 in older compilers.

gcc/c/
	* c-decl.cc (std_attribute_table): Add extra braces to work
	around PR 16333 in older compilers.

gcc/cp/
	* tree.cc (cxx_gnu_attribute_table): Add extra braces to work
	around PR 16333 in older compilers.

gcc/d/
	* d-attribs.cc (d_langhook_common_attribute_table): Add extra braces
	to work around PR 16333 in older compilers.
	(d_langhook_gnu_attribute_table): Likewise.

gcc/fortran/
	* f95-lang.cc (gfc_gnu_attribute_table): Add extra braces to work
	around PR 16333 in older compilers.

gcc/jit/
	* dummy-frontend.cc (jit_gnu_attribute_table): Add extra braces
	to work around PR 16333 in older compilers.
	(jit_format_attribute_table): Likewise.

gcc/lto/
	* lto-lang.cc (lto_gnu_attribute_table): Add extra braces to work
	around PR 16333 in older compilers.
	(lto_format_attribute_table): Likewise.
---
 gcc/ada/gcc-interface/utils.cc  | 2 +-
 gcc/attribs.cc                  | 2 +-
 gcc/c-family/c-attribs.cc       | 4 ++--
 gcc/c/c-decl.cc                 | 2 +-
 gcc/config/arm/arm.cc           | 2 +-
 gcc/config/i386/i386-options.cc | 2 +-
 gcc/config/ia64/ia64.cc         | 2 +-
 gcc/config/rs6000/rs6000.cc     | 2 +-
 gcc/cp/tree.cc                  | 7 +++++--
 gcc/d/d-attribs.cc              | 4 ++--
 gcc/fortran/f95-lang.cc         | 2 +-
 gcc/genhooks.cc                 | 7 ++++++-
 gcc/jit/dummy-frontend.cc       | 4 ++--
 gcc/langhooks-def.h             | 4 ++--
 gcc/lto/lto-lang.cc             | 4 ++--
 gcc/target-def.h                | 2 +-
 gcc/target.def                  | 2 +-
 17 files changed, 31 insertions(+), 23 deletions(-)

diff --git a/gcc/ada/gcc-interface/utils.cc b/gcc/ada/gcc-interface/utils.cc
index f46454d6545..6629d3f9b18 100644
--- a/gcc/ada/gcc-interface/utils.cc
+++ b/gcc/ada/gcc-interface/utils.cc
@@ -221,7 +221,7 @@ static const attribute_spec gnat_internal_attributes[] =
 
 const scoped_attribute_specs gnat_internal_attribute_table =
 {
-  "gnu", gnat_internal_attributes
+  "gnu", { gnat_internal_attributes }
 };
 
 /* Associates a GNAT tree node to a GCC tree node. It is used in
diff --git a/gcc/attribs.cc b/gcc/attribs.cc
index eff99002fbb..1e6369a47fe 100644
--- a/gcc/attribs.cc
+++ b/gcc/attribs.cc
@@ -302,7 +302,7 @@ handle_ignored_attributes_option (vec<char *> *v)
 	  attrs = { table, 1 };
 	}
       const scoped_attribute_specs scoped_specs = {
-	IDENTIFIER_POINTER (vendor_id), attrs
+	IDENTIFIER_POINTER (vendor_id), { attrs }
       };
       register_scoped_attributes (scoped_specs, attrs.empty ());
     }
diff --git a/gcc/c-family/c-attribs.cc b/gcc/c-family/c-attribs.cc
index 45af07453ea..859dcf255ba 100644
--- a/gcc/c-family/c-attribs.cc
+++ b/gcc/c-family/c-attribs.cc
@@ -584,7 +584,7 @@ const struct attribute_spec c_common_gnu_attributes[] =
 
 const struct scoped_attribute_specs c_common_gnu_attribute_table =
 {
-  "gnu", c_common_gnu_attributes
+  "gnu", { c_common_gnu_attributes }
 };
 
 /* Give the specifications for the format attributes, used by C and all
@@ -603,7 +603,7 @@ const struct attribute_spec c_common_format_attributes[] =
 
 const struct scoped_attribute_specs c_common_format_attribute_table =
 {
-  "gnu", c_common_format_attributes
+  "gnu", { c_common_format_attributes }
 };
 
 /* Returns TRUE iff the attribute indicated by ATTR_ID takes a plain
diff --git a/gcc/c/c-decl.cc b/gcc/c/c-decl.cc
index 248d1bb3206..92c83e1bf10 100644
--- a/gcc/c/c-decl.cc
+++ b/gcc/c/c-decl.cc
@@ -4653,7 +4653,7 @@ static const attribute_spec std_attributes[] =
 
 const scoped_attribute_specs std_attribute_table =
 {
-  nullptr, std_attributes
+  nullptr, { std_attributes }
 };
 
 /* Create the predefined scalar types of C,
diff --git a/gcc/config/arm/arm.cc b/gcc/config/arm/arm.cc
index 5cb35e8d061..da5cda225f1 100644
--- a/gcc/config/arm/arm.cc
+++ b/gcc/config/arm/arm.cc
@@ -385,7 +385,7 @@ static const attribute_spec arm_gnu_attributes[] =
 
 static const scoped_attribute_specs arm_gnu_attribute_table =
 {
-  "gnu", arm_gnu_attributes
+  "gnu", { arm_gnu_attributes }
 };
 
 static const scoped_attribute_specs *const arm_attribute_table[] =
diff --git a/gcc/config/i386/i386-options.cc b/gcc/config/i386/i386-options.cc
index 877659229d2..f86ad332aad 100644
--- a/gcc/config/i386/i386-options.cc
+++ b/gcc/config/i386/i386-options.cc
@@ -4171,7 +4171,7 @@ static const attribute_spec ix86_gnu_attributes[] =
 
 const scoped_attribute_specs ix86_gnu_attribute_table =
 {
-  "gnu", ix86_gnu_attributes
+  "gnu", { ix86_gnu_attributes }
 };
 
 #include "gt-i386-options.h"
diff --git a/gcc/config/ia64/ia64.cc b/gcc/config/ia64/ia64.cc
index f7766c25622..ac566efcf19 100644
--- a/gcc/config/ia64/ia64.cc
+++ b/gcc/config/ia64/ia64.cc
@@ -375,7 +375,7 @@ static const attribute_spec ia64_gnu_attributes[] =
 
 static const scoped_attribute_specs ia64_gnu_attribute_table =
 {
-  "gnu", ia64_gnu_attributes
+  "gnu", { ia64_gnu_attributes }
 };
 
 static const scoped_attribute_specs *const ia64_attribute_table[] =
diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
index 5386470f6f8..3801afe2c95 100644
--- a/gcc/config/rs6000/rs6000.cc
+++ b/gcc/config/rs6000/rs6000.cc
@@ -1276,7 +1276,7 @@ static const attribute_spec rs6000_gnu_attributes[] =
 
 static const scoped_attribute_specs rs6000_gnu_attribute_table =
 {
-  "gnu", rs6000_gnu_attributes
+  "gnu", { rs6000_gnu_attributes }
 };
 
 static const scoped_attribute_specs *const rs6000_attribute_table[] =
diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc
index e0b9d512adc..da4d5c51f07 100644
--- a/gcc/cp/tree.cc
+++ b/gcc/cp/tree.cc
@@ -5098,7 +5098,7 @@ static const attribute_spec cxx_gnu_attributes[] =
 
 const scoped_attribute_specs cxx_gnu_attribute_table =
 {
-  "gnu", cxx_gnu_attributes
+  "gnu", { cxx_gnu_attributes }
 };
 
 /* Table of C++ standard attributes.  */
@@ -5126,7 +5126,10 @@ static const attribute_spec std_attributes[] =
     handle_contract_attribute, NULL }
 };
 
-const scoped_attribute_specs std_attribute_table = { nullptr, std_attributes };
+const scoped_attribute_specs std_attribute_table =
+{
+  nullptr, { std_attributes }
+};
 
 /* Handle an "init_priority" attribute; arguments as in
    struct attribute_spec.handler.  */
diff --git a/gcc/d/d-attribs.cc b/gcc/d/d-attribs.cc
index f6411058072..3b69c530c1d 100644
--- a/gcc/d/d-attribs.cc
+++ b/gcc/d/d-attribs.cc
@@ -194,7 +194,7 @@ static const attribute_spec d_langhook_common_attributes[] =
 
 const scoped_attribute_specs d_langhook_common_attribute_table =
 {
-  "gnu", d_langhook_common_attributes
+  "gnu", { d_langhook_common_attributes }
 };
 
 /* Table of D language attributes exposed by `gcc.attribute' UDAs.  */
@@ -246,7 +246,7 @@ static const attribute_spec d_langhook_gnu_attributes[] =
 
 const scoped_attribute_specs d_langhook_gnu_attribute_table =
 {
-  "gnu", d_langhook_gnu_attributes
+  "gnu", { d_langhook_gnu_attributes }
 };
 
 /* Insert the type attribute ATTRNAME with value VALUE into TYPE.
diff --git a/gcc/fortran/f95-lang.cc b/gcc/fortran/f95-lang.cc
index 99dd76226a2..32fddcde957 100644
--- a/gcc/fortran/f95-lang.cc
+++ b/gcc/fortran/f95-lang.cc
@@ -102,7 +102,7 @@ static const attribute_spec gfc_gnu_attributes[] =
 
 static const scoped_attribute_specs gfc_gnu_attribute_table =
 {
-  "gnu", gfc_gnu_attributes
+  "gnu", { gfc_gnu_attributes }
 };
 
 static const scoped_attribute_specs *const gfc_attribute_table[] =
diff --git a/gcc/genhooks.cc b/gcc/genhooks.cc
index 49414eca531..135c523bd00 100644
--- a/gcc/genhooks.cc
+++ b/gcc/genhooks.cc
@@ -304,7 +304,12 @@ emit_init_macros (const char *docname)
 		      name, name, hook_array[i].init);
 	    }
 	  if (nest == print_nest)
-	    printf ("    %s, \\\n", name);
+	    {
+	      if (strcmp (name, "TARGET_ATTRIBUTE_TABLE") == 0)
+		printf ("    { %s }, \\\n", name);
+	      else
+		printf ("    %s, \\\n", name);
+	    }
 	}
     }
 }
diff --git a/gcc/jit/dummy-frontend.cc b/gcc/jit/dummy-frontend.cc
index 61cc0e1ae66..1ea6ad382d8 100644
--- a/gcc/jit/dummy-frontend.cc
+++ b/gcc/jit/dummy-frontend.cc
@@ -133,7 +133,7 @@ static const attribute_spec jit_gnu_attributes[] =
 
 static const scoped_attribute_specs jit_gnu_attribute_table =
 {
-  "gnu", jit_gnu_attributes
+  "gnu", { jit_gnu_attributes }
 };
 
 /* Give the specifications for the format attributes, used by C and all
@@ -151,7 +151,7 @@ static const attribute_spec jit_format_attributes[] =
 
 static const scoped_attribute_specs jit_format_attribute_table =
 {
-  "gnu", jit_format_attributes
+  "gnu", { jit_format_attributes }
 };
 
 static const scoped_attribute_specs *const jit_attribute_table[] =
diff --git a/gcc/langhooks-def.h b/gcc/langhooks-def.h
index c9cb65759c2..042fd0174e3 100644
--- a/gcc/langhooks-def.h
+++ b/gcc/langhooks-def.h
@@ -153,7 +153,7 @@ extern const char *lhd_get_sarif_source_language (const char *);
 #define LANG_HOOKS_GET_SARIF_SOURCE_LANGUAGE lhd_get_sarif_source_language
 
 /* Attribute hooks.  */
-#define LANG_HOOKS_ATTRIBUTE_TABLE		{}
+#define LANG_HOOKS_ATTRIBUTE_TABLE
 
 /* Tree inlining hooks.  */
 #define LANG_HOOKS_TREE_INLINING_VAR_MOD_TYPE_P \
@@ -364,7 +364,7 @@ extern void lhd_end_section (void);
   LANG_HOOKS_TYPES_COMPATIBLE_P, \
   LANG_HOOKS_PRINT_ERROR_FUNCTION, \
   LANG_HOOKS_TO_TARGET_CHARSET, \
-  LANG_HOOKS_ATTRIBUTE_TABLE, \
+  { LANG_HOOKS_ATTRIBUTE_TABLE }, \
   LANG_HOOKS_TREE_INLINING_INITIALIZER, \
   LANG_HOOKS_TREE_DUMP_INITIALIZER, \
   LANG_HOOKS_DECLS, \
diff --git a/gcc/lto/lto-lang.cc b/gcc/lto/lto-lang.cc
index 41de35a9ff6..62aaa9b7d10 100644
--- a/gcc/lto/lto-lang.cc
+++ b/gcc/lto/lto-lang.cc
@@ -140,7 +140,7 @@ static const attribute_spec lto_gnu_attributes[] =
 
 static const scoped_attribute_specs lto_gnu_attribute_table =
 {
-  "gnu", lto_gnu_attributes
+  "gnu", { lto_gnu_attributes }
 };
 
 /* Give the specifications for the format attributes, used by C and all
@@ -158,7 +158,7 @@ static const attribute_spec lto_format_attributes[] =
 
 static const scoped_attribute_specs lto_format_attribute_table =
 {
-  "gnu", lto_format_attributes
+  "gnu", { lto_format_attributes }
 };
 
 static const scoped_attribute_specs *const lto_attribute_table[] =
diff --git a/gcc/target-def.h b/gcc/target-def.h
index d03b039ab24..79fe8e28e7e 100644
--- a/gcc/target-def.h
+++ b/gcc/target-def.h
@@ -129,7 +129,7 @@
 
 #define TARGET_GNU_ATTRIBUTES(NAME, ...) \
   static const attribute_spec NAME##_2[] = __VA_ARGS__; \
-  static const scoped_attribute_specs NAME##_1 = { "gnu", NAME##_2 }; \
+  static const scoped_attribute_specs NAME##_1 = { "gnu", { NAME##_2 } }; \
   static const scoped_attribute_specs *const NAME[] = { &NAME##_1 }
 
 #include "target-hooks-def.h"
diff --git a/gcc/target.def b/gcc/target.def
index c6562ed40ac..2c85be235e4 100644
--- a/gcc/target.def
+++ b/gcc/target.def
@@ -2247,7 +2247,7 @@ TARGET_GNU_ATTRIBUTES (@var{cpu_attribute_table}, @{\n\
   @{ \"@var{attributen}\", @dots{} @},\n\
 @});\n\
 @end smallexample",
- array_slice<const struct scoped_attribute_specs *const>, {})
+ array_slice<const struct scoped_attribute_specs *const>,)
 
 /* Return true iff attribute NAME expects a plain identifier as its first
    argument.  */
-- 
2.25.1