f36306502
Denis Vlasenko
2007-03-20
Subject
small doc update
Binary
No binary (build failed)
Architecture & Compiler Flags
—
Build Log
(log yok)
Commit Diff GitHub →
docs/keep_data_small.txt+13 -7
| @@ -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. |