On 01/15/2016 02:01 PM, Jason Merrill wrote:
On 01/14/2016 10:01 PM, Martin Sebor wrote:
In anticipation of needing to do something I put together the attached
patch that rolls this change into version 10, letting version 9 and
prior roll it back. I also mention it in the manual. What the patch
doesn't do is add a warning.
Looks good, but please also add a warning. See the use of
abi_warn_or_compat_version_crosses elsewhere in mangle.c.
Attached is an updated patch with the warning plus a test for it.
The test depends on the fix that I posted yesterday for #69317 -
[6 regression] wrong ABI version in -Wabi warning.
Martin
gcc/testsuite/ChangeLog:
2016-01-14 Martin Sebor <mse...@redhat.com>
PR c++/69277
* gcc/testsuite/g++.dg/abi/flexarray-abi-v9.C: New test.
* g++.dg/ext/flexarray-mangle-2.C: New test.
* g++.dg/ext/flexarray-mangle.C: New test.
* g++.dg/abi/flexarray-Wabi-9-10.C: New test.
gcc/cp/ChangeLog:
2016-01-14 Martin Sebor <mse...@redhat.com>
PR c++/69277
* mangle.c (write_array_type): Mangle flexible array members
the same as arrays with an unspecified size.
gcc/ChangeLog:
2016-01-14 Martin Sebor <mse...@redhat.com>
PR c++/69277
* invoke.texi (-fabi-version=, -Wabi): Update version 10.
Index: gcc/cp/mangle.c
===================================================================
--- gcc/cp/mangle.c (revision 232296)
+++ gcc/cp/mangle.c (working copy)
@@ -3280,8 +3280,10 @@ write_template_template_arg (const tree
::= A <expression> _ </element/ type>
"Array types encode the dimension (number of elements) and the
- element type. For variable length arrays, the dimension (but not
- the '_' separator) is omitted." */
+ element type. For variable length arrays, the dimension (but not
+ the '_' separator) is omitted."
+ Note that for flexible array members, like for other arrays of
+ unspecified size, the dimension is also omitted. */
static void
write_array_type (const tree type)
@@ -3289,30 +3291,42 @@ write_array_type (const tree type)
write_char ('A');
if (TYPE_DOMAIN (type))
{
- tree index_type;
- tree max;
-
- index_type = TYPE_DOMAIN (type);
- /* The INDEX_TYPE gives the upper and lower bounds of the
- array. */
- max = TYPE_MAX_VALUE (index_type);
- if (TREE_CODE (max) == INTEGER_CST)
+ tree index_type = TYPE_DOMAIN (type);
+ /* The INDEX_TYPE gives the upper and lower bounds of the array.
+ It's null for flexible array members which have no upper bound
+ (this is a change from GCC 5 and prior where such members were
+ incorrectly mangled as zero-length arrays). */
+ if (tree max = TYPE_MAX_VALUE (index_type))
{
- /* The ABI specifies that we should mangle the number of
- elements in the array, not the largest allowed index. */
- offset_int wmax = wi::to_offset (max) + 1;
- /* Truncate the result - this will mangle [0, SIZE_INT_MAX]
- number of elements as zero. */
- wmax = wi::zext (wmax, TYPE_PRECISION (TREE_TYPE (max)));
- gcc_assert (wi::fits_uhwi_p (wmax));
- write_unsigned_number (wmax.to_uhwi ());
+ if (TREE_CODE (max) == INTEGER_CST)
+ {
+ /* The ABI specifies that we should mangle the number of
+ elements in the array, not the largest allowed index. */
+ offset_int wmax = wi::to_offset (max) + 1;
+ /* Truncate the result - this will mangle [0, SIZE_INT_MAX]
+ number of elements as zero. */
+ wmax = wi::zext (wmax, TYPE_PRECISION (TREE_TYPE (max)));
+ gcc_assert (wi::fits_uhwi_p (wmax));
+ write_unsigned_number (wmax.to_uhwi ());
+ }
+ else
+ {
+ max = TREE_OPERAND (max, 0);
+ write_expression (max);
+ }
}
else
- {
- max = TREE_OPERAND (max, 0);
- write_expression (max);
- }
+ {
+ if (!abi_version_at_least (10))
+ {
+ /* In ABI versions prior to 10 mangle flexible array members
+ the same as zero-length arrays for compatibility. */
+ write_unsigned_number (0);
+ }
+ if (abi_warn_or_compat_version_crosses (10))
+ G.need_abi_warning = true;
+ }
}
write_char ('_');
write_type (TREE_TYPE (type));
Index: gcc/doc/invoke.texi
===================================================================
--- gcc/doc/invoke.texi (revision 232296)
+++ gcc/doc/invoke.texi (working copy)
@@ -2173,7 +2173,8 @@ Version 9, which first appeared in G++ 5
Version 10, which first appeared in G++ 6.1, adds mangling of
attributes that affect type identity, such as ia32 calling convention
-attributes (e.g. @samp{stdcall}).
+attributes (e.g. @samp{stdcall}). This version also corrects the mangling
+of flexible array members.
See also @option{-Wabi}.
@@ -2605,16 +2606,16 @@ have meanings only for C++ programs:
@item -Wabi @r{(C, Objective-C, C++ and Objective-C++ only)}
@opindex Wabi
@opindex Wno-abi
-Warn when G++ it generates code that is probably not compatible with
-the vendor-neutral C++ ABI@. Since G++ now defaults to updating the
+Warn when G++ generates code that is probably not compatible with
+the vendor-neutral C++ ABI. Since G++ defaults to updating the
ABI with each major release, normally @option{-Wabi} will warn only if
there is a check added later in a release series for an ABI issue
discovered since the initial release. @option{-Wabi} will warn about
-more things if an older ABI version is selected (with
+more changes if an older ABI version is selected (with
@option{-fabi-version=@var{n}}).
@option{-Wabi} can also be used with an explicit version number to
-warn about compatibility with a particular @option{-fabi-version}
+warn about incompatibility with a particular @option{-fabi-version}
level, e.g. @option{-Wabi=2} to warn about changes relative to
@option{-fabi-version=2}.
@@ -2703,7 +2704,11 @@ ia32 calling conventions on a function t
did not affect the mangled name, leading to name collisions when
function pointers were used as template arguments.
-This was fixed in @option{-fabi-version=10}, the default for GCC 6.1.
+Flexible array members were mangled as zero-length arrays rather than
+as arrays of unspecified size as expected.
+
+These problems were fixed in @option{-fabi-version=10}, the default
+for GCC 6.1.
@end itemize
Index: gcc/testsuite/g++.dg/ext/flexarray-mangle-2.C
===================================================================
--- gcc/testsuite/g++.dg/ext/flexarray-mangle-2.C (revision 0)
+++ gcc/testsuite/g++.dg/ext/flexarray-mangle-2.C (working copy)
@@ -0,0 +1,48 @@
+// PR c++/69277 - [6 Regression] ICE mangling a flexible array member
+// { dg-do compile { target c++11 } }
+
+struct A {
+ int n;
+ char a [];
+};
+
+// Declare but do not define function templates.
+template <class T>
+void foo ();
+
+template <typename T>
+void fooref (T&);
+
+// Rvalue references are a C++ 11 feature.
+template <typename T>
+void foorefref (T&&);
+
+void bar (A a)
+{
+ // Decltype is also a C++ 11 feature.
+ // Verify that decltype gets the right type and that foo is
+ // mangled correctly.
+ foo<decltype (a.a)>();
+
+ // Verify that function templates taking a reference and an rvalue
+ // references (as in PR c++/69277) are also mangled correctly.
+ fooref (a.a);
+ foorefref (a.a);
+}
+
+// In G++ versions prior to 6 (ABI version 9 and prior), flexible array
+// members were incorrectly mangled as arrays of zero elements. Verify
+// that flexible array members are mangled correctly as arrays of
+// an unspecified number of elements by default (ABI version 10 and
+// newer). See g++.dg/abi/flexarray-abi-v9.C for the compatibility
+// test.
+
+// void foo<char []>():
+// { dg-final { scan-assembler _Z3fooIA_cEvv } }
+
+// The following is derived from PR c++/69277:
+// void fooref<char []>(char (&) [])
+// { dg-final { scan-assembler _Z6foorefIA_cEvRT_ } }
+
+// void foorefref<char (&) []>(char (&) [])
+// { dg-final { scan-assembler _Z9foorefrefIRA_cEvOT_ } }
Index: gcc/testsuite/g++.dg/ext/flexarray-mangle.C
===================================================================
--- gcc/testsuite/g++.dg/ext/flexarray-mangle.C (revision 0)
+++ gcc/testsuite/g++.dg/ext/flexarray-mangle.C (working copy)
@@ -0,0 +1,26 @@
+// PR c++/69277 - [6 Regression] ICE mangling a flexible array member
+// { dg-do compile }
+
+struct A {
+ int n;
+ char a [];
+};
+
+// Declare but do not define function templates.
+template <typename T>
+void fooref (T&);
+
+void bar (A a)
+{
+ fooref (a.a);
+}
+
+// In G++ versions prior to 6 (ABI version 9 and prior), flexible array
+// members were incorrectly mangled as arrays of zero elements. Verify
+// that flexible array members are mangled correctly as arrays of
+// an unspecified number of elements by default (ABI version 10 and
+// newer). See g++.dg/abi/flexarray-abi-v9.C for the compatibility
+// test.
+
+// void fooref<char []>(char (&) [])
+// { dg-final { scan-assembler _Z6foorefIA_cEvRT_ } }
Index: gcc/testsuite/g++.dg/abi/flexarray-abi-v9.C
===================================================================
--- gcc/testsuite/g++.dg/abi/flexarray-abi-v9.C (revision 0)
+++ gcc/testsuite/g++.dg/abi/flexarray-abi-v9.C (working copy)
@@ -0,0 +1,49 @@
+// Test to verify ABI version 9 (and prior) compatibility mangling
+// of a flexible array member. See also PR c++/69277.
+// { dg-do compile { target c++11 } }
+// { dg-options "-fabi-version=9" }
+
+struct A {
+ int n;
+ char a [];
+};
+
+// Declare but do not define function templates.
+template <class T>
+void foo ();
+
+template <typename T>
+void fooref (T&);
+
+// Rvalue references are a C++ 11 feature.
+template <typename T>
+void foorefref (T&&);
+
+void bar (A a)
+{
+ // Decltype is also a C++ 11 feature.
+ // Verify that decltype gets the right type and that foo is
+ // mangled correctly.
+ foo<decltype (a.a)>();
+
+ // Verify that function templates taking a reference and an rvalue
+ // references (as in PR c++/69277) are also mangled correctly.
+ fooref (a.a);
+ foorefref (a.a);
+}
+
+// In G++ versions prior to 6 (ABI version 10), flexible array members
+// were incorrectly mangled as arrays of zero elements. Verify that
+// they are still mangled that way with -fabi-version=9 (i.e., unless
+// -fabi-version=10 is used. See g++.dg/ext/flexarray-mangle-3.C
+// for that test.)
+
+// void foo<char [0]>():
+// { dg-final { scan-assembler _Z3fooIA0_cEvv } }
+
+// The following is derived from PR c++/69277:
+// void fooref<char [0]>(char (&) [0])
+// { dg-final { scan-assembler _Z6foorefIA0_cEvRT_ } }
+
+// void foorefref<char (&) [0]>(char (&) [0])
+// { dg-final { scan-assembler _Z9foorefrefIRA0_cEvOT_ } }
Index: gcc/testsuite/g++.dg/abi/flexarray-Wabi-9-10.C
===================================================================
--- gcc/testsuite/g++.dg/abi/flexarray-Wabi-9-10.C (revision 0)
+++ gcc/testsuite/g++.dg/abi/flexarray-Wabi-9-10.C (working copy)
@@ -0,0 +1,23 @@
+// Test to verify that -Wabi issues a warning for the change in
+// how flexible array members are mangled between ABI versions
+// 9 and 10. See also PR c++/69277.
+// { dg-do compile }
+// { dg-options "-Wabi=9 -fabi-version=10" }
+
+struct A {
+ int n;
+ char a [];
+};
+
+// In G++ versions prior to 6 (ABI version 10), flexible array members
+// were incorrectly mangled as arrays of zero elements. Verify that
+// the -Wabi=9 option elicits a warning pointing out the change in
+// how they get mangled in version 10 and later.
+//
+template <typename T>
+void foo (T&) { } // { dg-warning "the mangled name of .void foo\\(T&\\) \\\[with T = char \\\[\\\]\\\]. changed between -fabi-version=10 \\(_Z3fooIA0_cEvRT_\\) and -fabi-version=9 \\(_Z3fooIA_cEvRT_\\)" }
+
+void bar (A *a)
+{
+ foo (a->a);
+}
