[C PATCH] Don't reject valid code with _Alignas (PR c/61053)
Marek Polacek
polacek@redhat.com
Mon May 5 20:27:00 GMT 2014
In this PR the issue is that we reject (valid) code such as
_Alignas (long long) long long foo;
with -m32, because we trip this condition:
alignas_align = 1U << declspecs->align_log;
if (alignas_align < TYPE_ALIGN_UNIT (type))
{
if (name)
error_at (loc, "%<_Alignas%> specifiers cannot reduce "
"alignment of %qE", name);
and error later on, since alignas_align is 4 (correct, see PR52023 for
why), but TYPE_ALIGN_UNIT of long long is 8. I think TYPE_ALIGN_UNIT
is wrong here as that won't give us minimal alignment required.
In c_sizeof_or_alignof_type we already have the code to compute such
minimal alignment so I just moved the code to a separate function
and used that instead of TYPE_ALIGN_UNIT.
Note that the test is run only on i?86 and x86_64, because we can't (?)
easily determine which target requires what alignment.
Regtested/bootstrapped on x86_64-unknown-linux-gnu and
powerpc64-unknown-linux-gnu, ok for trunk?
2014-05-05 Marek Polacek <polacek@redhat.com>
PR c/61053
c-family/
* c-common.c (min_align_of_type): New function factored out from...
(c_sizeof_or_alignof_type): ...here.
* c-common.h (min_align_of_type): Declare.
c/
* c-decl.c (grokdeclarator): Use min_align_of_type instead of
TYPE_ALIGN_UNIT.
testsuite/
* gcc.dg/pr61053.c: New test.
diff --git gcc/c-family/c-common.c gcc/c-family/c-common.c
index 0ad955d..6d4440e 100644
--- gcc/c-family/c-common.c
+++ gcc/c-family/c-common.c
@@ -4931,6 +4931,26 @@ c_common_get_alias_set (tree t)
return -1;
}
+/* Return the least alignment required for type TYPE. */
+
+unsigned int
+min_align_of_type (tree type)
+{
+ unsigned int align = TYPE_ALIGN (type);
+ align = MIN (align, BIGGEST_ALIGNMENT);
+#ifdef BIGGEST_FIELD_ALIGNMENT
+ align = MIN (align, BIGGEST_FIELD_ALIGNMENT);
+#endif
+ unsigned int field_align = align;
+#ifdef ADJUST_FIELD_ALIGN
+ tree field = build_decl (UNKNOWN_LOCATION, FIELD_DECL, NULL_TREE,
+ type);
+ field_align = ADJUST_FIELD_ALIGN (field, field_align);
+#endif
+ align = MIN (align, field_align);
+ return align / BITS_PER_UNIT;
+}
+
/* Compute the value of 'sizeof (TYPE)' or '__alignof__ (TYPE)', where
the IS_SIZEOF parameter indicates which operator is being applied.
The COMPLAIN flag controls whether we should diagnose possibly
@@ -5009,21 +5029,7 @@ c_sizeof_or_alignof_type (location_t loc,
size_int (TYPE_PRECISION (char_type_node)
/ BITS_PER_UNIT));
else if (min_alignof)
- {
- unsigned int align = TYPE_ALIGN (type);
- align = MIN (align, BIGGEST_ALIGNMENT);
-#ifdef BIGGEST_FIELD_ALIGNMENT
- align = MIN (align, BIGGEST_FIELD_ALIGNMENT);
-#endif
- unsigned int field_align = align;
-#ifdef ADJUST_FIELD_ALIGN
- tree field = build_decl (UNKNOWN_LOCATION, FIELD_DECL, NULL_TREE,
- type);
- field_align = ADJUST_FIELD_ALIGN (field, field_align);
-#endif
- align = MIN (align, field_align);
- value = size_int (align / BITS_PER_UNIT);
- }
+ value = size_int (min_align_of_type (type));
else
value = size_int (TYPE_ALIGN_UNIT (type));
}
diff --git gcc/c-family/c-common.h gcc/c-family/c-common.h
index 57b7dce..d34d2bb 100644
--- gcc/c-family/c-common.h
+++ gcc/c-family/c-common.h
@@ -758,6 +758,7 @@ extern tree c_wrap_maybe_const (tree, bool);
extern tree c_save_expr (tree);
extern tree c_common_truthvalue_conversion (location_t, tree);
extern void c_apply_type_quals_to_decl (int, tree);
+extern unsigned int min_align_of_type (tree);
extern tree c_sizeof_or_alignof_type (location_t, tree, bool, bool, int);
extern tree c_alignof_expr (location_t, tree);
/* Print an error message for invalid operands to arith operation CODE.
diff --git gcc/c/c-decl.c gcc/c/c-decl.c
index 6e7c589..9f7419a 100644
--- gcc/c/c-decl.c
+++ gcc/c/c-decl.c
@@ -5931,7 +5931,7 @@ grokdeclarator (const struct c_declarator *declarator,
else if (declspecs->align_log != -1)
{
alignas_align = 1U << declspecs->align_log;
- if (alignas_align < TYPE_ALIGN_UNIT (type))
+ if (alignas_align < min_align_of_type (type))
{
if (name)
error_at (loc, "%<_Alignas%> specifiers cannot reduce "
diff --git gcc/testsuite/gcc.dg/pr61053.c gcc/testsuite/gcc.dg/pr61053.c
index e69de29..e3db534 100644
--- gcc/testsuite/gcc.dg/pr61053.c
+++ gcc/testsuite/gcc.dg/pr61053.c
@@ -0,0 +1,75 @@
+/* PR c/61053 */
+/* { dg-do compile { target i?86-*-* x86_64-*-* } } */
+/* { dg-options "-std=c11 -pedantic-errors" } */
+
+_Alignas (char) char cc;
+_Alignas (short int) char cs;
+_Alignas (int) char ci;
+_Alignas (long int) char cl;
+_Alignas (long long int) char cll;
+_Alignas (float) char cf;
+_Alignas (double) char cd;
+_Alignas (long double) char cld;
+
+_Alignas (char) short int sc; /* { dg-error "cannot reduce alignment" } */
+_Alignas (short int) short int ss;
+_Alignas (int) short int si;
+_Alignas (long int) short int sl;
+_Alignas (long long int) short int sll;
+_Alignas (float) short int sf;
+_Alignas (double) short int sd;
+_Alignas (long double) short int sld;
+
+_Alignas (char) int ic; /* { dg-error "cannot reduce alignment" } */
+_Alignas (short int) int is; /* { dg-error "cannot reduce alignment" } */
+_Alignas (int) int ii;
+_Alignas (long int) int il;
+_Alignas (long long int) int ill;
+_Alignas (float) int if_;
+_Alignas (double) int id;
+_Alignas (long double) int ild;
+
+_Alignas (char) long int lic; /* { dg-error "cannot reduce alignment" } */
+_Alignas (short int) long int lis; /* { dg-error "cannot reduce alignment" } */
+_Alignas (int) long int lii; /* { dg-error "cannot reduce alignment" "" { target { lp64 } } } */
+_Alignas (long int) long int lil;
+_Alignas (long long int) long int lill;
+_Alignas (float) long int lif; /* { dg-error "cannot reduce alignment" "" { target { lp64 } } } */
+_Alignas (double) long int lid;
+_Alignas (long double) long int lild;
+
+_Alignas (char) long long int llic; /* { dg-error "cannot reduce alignment" } */
+_Alignas (short int) long long int llis; /* { dg-error "cannot reduce alignment" } */
+_Alignas (int) long long int llii; /* { dg-error "cannot reduce alignment" "" { target { lp64 } } } */
+_Alignas (long int) long long int llil;
+_Alignas (long long int) long long int llill;
+_Alignas (float) long long int llif; /* { dg-error "cannot reduce alignment" "" { target { lp64 } } } */
+_Alignas (double) long long int llid;
+_Alignas (long double) long long int llild;
+
+_Alignas (char) float fc; /* { dg-error "cannot reduce alignment" } */
+_Alignas (short int) float fs; /* { dg-error "cannot reduce alignment" } */
+_Alignas (int) float fi;
+_Alignas (long int) float fl;
+_Alignas (long long int) float fll;
+_Alignas (float) float ff;
+_Alignas (double) float fd;
+_Alignas (long double) float fld;
+
+_Alignas (char) double dc; /* { dg-error "cannot reduce alignment" } */
+_Alignas (short int) double ds; /* { dg-error "cannot reduce alignment" } */
+_Alignas (int) double di; /* { dg-error "cannot reduce alignment" "" { target { lp64 } } } */
+_Alignas (long int) double dl;
+_Alignas (long long int) double dll;
+_Alignas (float) double df; /* { dg-error "cannot reduce alignment" "" { target { lp64 } } } */
+_Alignas (double) double dd;
+_Alignas (long double) double dld;
+
+_Alignas (char) long double ldc; /* { dg-error "cannot reduce alignment" } */
+_Alignas (short int) long double lds; /* { dg-error "cannot reduce alignment" } */
+_Alignas (int) long double ldi; /* { dg-error "cannot reduce alignment" "" { target { lp64 } } } */
+_Alignas (long int) long double ldl; /* { dg-error "cannot reduce alignment" "" { target { lp64 } } } */
+_Alignas (long long int) long double ldll; /* { dg-error "cannot reduce alignment" "" { target { lp64 } } } */
+_Alignas (float) long double ldf; /* { dg-error "cannot reduce alignment" "" { target { lp64 } } } */
+_Alignas (double) long double ldd; /* { dg-error "cannot reduce alignment" "" { target { lp64 } } } */
+_Alignas (long double) long double ldld;
Marek
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