Summary:
Change the condition of this unnecessary packed warning. The packed is unnecessary when
1. the alignment of the struct/class won't alter.
2. the size is unchanged.
3. the offset of each field is the same.
Remove all field-level warning.
Reviewers: chh, akyrtzi, rtrieu
Reviewed By: chh
Subscribers: rsmith, srhines, cfe-commits, xazax.hun
Differential Revision: https://reviews.llvm.org/D34114
llvm-svn: 309750
someone thought all the bits would be value bits in this case.
Also fix the wording of the warning -- it claimed that the width of 'bool' is
8, which is not correct; the width is 1 bit, whereas the size is 8 bits in our
implementation.
llvm-svn: 248435
-Wpadded warns when undesired padding is introduced in a struct. (rdar://7469556)
-Wpacked warns if a struct is given the packed attribute, but the packed attribute has no effect
on the layout or the size of the struct. Such structs may be mis-aligned for little benefit.
The warnings are emitted at the point where layout is calculated, that is at RecordLayoutBuilder.
To avoid calculating the layouts of all structs regardless of whether they are needed or not,
I let the layouts be lazily constructed when needed. This has the disadvantage that the above warnings
will be emitted only when they are used for IR gen, and not e.g with -fsyntax-only:
$ cat t.c
struct S {
char c;
int i;
};
void f(struct S* s) {}
$ clang -fsyntax-only -Wpadded t.c
$ clang -c -Wpadded t.c -o t.o
t.c:3:7: warning: padding struct 'struct S' with 3 bytes to align 'i' [-Wpadded]
int i;
^
1 warning generated.
This is a good tradeoff between providing the warnings and not calculating layouts for all
structs in case the user has enabled a couple of rarely used warnings.
llvm-svn: 114544
Yan Wang