My enhancement to improve the detection of attribute collisions
introduced a regression of sorts in the g++.dg/pr53037-4.C test
on ia64.
https://gcc.gnu.org/ml/gcc-testresults/2017-12/msg00672.html
The regression hasn't been noticed anywhere else only because
all the other targets apparently have no low limit on function
alignment, whereas ia64 has a limit of 32. As a result of
the limit the i64 compiler would issue not one but two errors
for a function declaration with attribute warn_if_not_aligned
that specifies a value less than 32:
one for the attribute itself (because it's not allowed on
functions),
and another for the lower value.
The attached patch fixes this by issuing the error only for
attribute aligned with a lower requirement but not attribute
warn_if_not_aligned.
I tried to come up with a test for this that would fail on
other targets besides ia64 (those with no low bound on
function alignment) but couldn't find a way to do it. If
someone knows of a way I'd be glad to add a better test
than pr53037-4.C.
Martin
gcc/c-family/ChangeLog:
* c-attribs.c (common_handle_aligned_attribute): Avoid issuing
an error for attribute warn_if_not_aligned.
diff --git a/gcc/c-family/c-attribs.c b/gcc/c-family/c-attribs.c
index 186df05..74c971d 100644
--- a/gcc/c-family/c-attribs.c
+++ b/gcc/c-family/c-attribs.c
@@ -1886,14 +1886,17 @@ common_handle_aligned_attribute (tree *node, tree name, tree args, int flags,
curalign /= BITS_PER_UNIT;
bitalign /= BITS_PER_UNIT;
+ bool diagd = true;
if (DECL_USER_ALIGN (decl) || DECL_USER_ALIGN (last_decl))
- warning (OPT_Wattributes,
- "ignoring attribute %<%E (%u)%> because it conflicts with "
- "attribute %<%E (%u)%>", name, bitalign, name, curalign);
- else
+ diagd = warning (OPT_Wattributes,
+ "ignoring attribute %<%E (%u)%> because it conflicts "
+ "with attribute %<%E (%u)%>",
+ name, bitalign, name, curalign);
+ else if (!warn_if_not_aligned_p)
+ /* Do not error out for attribute warn_if_not_aligned. */
error ("alignment for %q+D must be at least %d", decl, curalign);
- if (note)
+ if (diagd && note)
inform (DECL_SOURCE_LOCATION (last_decl), "previous declaration here");
*no_add_attrs = true;
