diff options
Diffstat (limited to 'docs/keep_data_small.txt')
| -rw-r--r-- | docs/keep_data_small.txt | 20 |
1 files changed, 13 insertions, 7 deletions
diff --git a/docs/keep_data_small.txt b/docs/keep_data_small.txt index 72de2d1..15e41ae 100644 --- a/docs/keep_data_small.txt +++ b/docs/keep_data_small.txt @@ -163,14 +163,20 @@ ridiculously large values. asm output diff for above example: gcc doesn't seem to have options for altering this behaviour. -gcc 3.4.3: +gcc 3.4.3 and 4.1.1 tested: +char c = 1; // gcc aligns to 32 bytes if sizeof(struct) >= 32 -struct st { - int c_iflag,c_oflag,c_cflag,c_lflag; - int i1,i2,i3; // struct will be aligned to 4 bytes -// int i1,i2,i3,i4; // struct will be aligned to 32 bytes -}; -struct st t = { 1 }; +struct { + int a,b,c,d; + int i1,i2,i3; +} s28 = { 1 }; // struct will be aligned to 4 bytes +struct { + int a,b,c,d; + int i1,i2,i3,i4; +} s32 = { 1 }; // struct will be aligned to 32 bytes // same for arrays char vc31[31] = { 1 }; // unaligned char vc32[32] = { 1 }; // aligned to 32 bytes + +-fpack-struct=1 reduces alignment of s28 to 1 (but probably will break layout +of many libc structs) but s32 and vc32 are still aligned to 32 bytes. |