struct tree_decl_common has
unsigned int align : 24;
And the maximum alignment we support is 1 << 23 bits (1 << 20 bytes). However,
config/elfos.h has
/* The biggest alignment supported by ELF in bits. 32-bit ELF
supports section alignment up to (0x80000000 * 8), while
64-bit ELF supports (0x8000000000000000 * 8). If this macro
is not defined, the default is the largest alignment supported
by 32-bit ELF and representable on a 32-bit host. Use this
macro to limit the alignment which can be specified using
the `__attribute__ ((aligned (N)))' construct. */
#ifndef MAX_OFILE_ALIGNMENT
#define MAX_OFILE_ALIGNMENT (((unsigned int) 1 << 28) * 8)
#endif
If we ask for alignment greater than 1 << 20 bytes, we won't
get any warnings:
[...@gnu-17 gcc]$ cat x.c
int foo __attribute__ ((aligned(1 << 21))) = 20;
int bar __attribute__ ((aligned(1 << 20))) = 20;
[...@gnu-17 gcc]$ ./xgcc -B./ -S x.i
[...@gnu-17 gcc]$ cat x.s
.file "x.i"
.globl foo
.data
.type foo, @object
.size foo, 4
foo:
.long 20
.globl bar
.align 1048576
.type bar, @object
.size bar, 4
bar:
.long 20
--
Summary: MAX_OFILE_ALIGNMENT in elfos.h is too big
Product: gcc
Version: 4.4.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: hjl dot tools at gmail dot com
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39323
