Bindgen fail to generate bindings for struct.

[Catramen]

Header:
#include <stdint.h>
typedef struct {
uint32_t f : 20;
uint8_t f1 : 4;
uint8_t f2 : 1;
uint8_t f3 : 1;
uint8_t f4 : 1;
uint8_t f5 : 5;
uint16_t f6;
uint8_t f7;
uint8_t f8;
uint8_t f9;
uint8_t f10;
uint8_t f11 : 2;
uint8_t f12 : 4;
uint16_t f13 : 10;
uint8_t f14;
uint32_t f15 : 19;
} S;

Bindgen command:
bindgen types.h -o t.rs
ERROR 2018-05-17T23:24:11Z: bindgen::codegen::struct_layout: Calculated wrong layout for S, too more 1 bytes

Bindgen version:
bindgen 0.36.1

[emilio]

Thanks for the report!

A bit reduced:

#include <stdint.h>
typedef struct {
  uint16_t f6;
  uint8_t f11 : 2;
  uint8_t f12 : 4;
  uint16_t f13 : 10;
  uint8_t f14;
  uint32_t f15 : 19;
} S;

[Catramen]

The size of:
typedef struct {
uint16_t f6;
uint8_t f11 : 2;
uint8_t f12 : 4;
uint16_t f13 : 10;
uint8_t f14;
uint32_t f15 : 19;
} S;
is 8. Which means the last bitfield is not aligned to u32.
But bindgen generates:
pub struct S {
pub f6: u16,
pub _bitfield_1: __BindgenBitfieldUnit<[u8; 2usize], u16>,
pub f14: u8,
pub _bitfield_2: __BindgenBitfieldUnit<[u8; 4usize], u32>,
pub __bindgen_align: [u32; 0usize],
}

We should have "pub _bitfield_2: __BindgenBitfieldUnit<[u8; 3usize], u8>,"
rather than "pub _bitfield_2: __BindgenBitfieldUnit<[u8; 4usize], u32>,"

[Catramen]

In section 6.7.2.1 #10 of C99 spec (http://www.dii.uchile.cl/~daespino/files/Iso_C_1999_definition.pdf):
The alignment of the addressable storage unit is unspecified.
Guess we should comply with clang implementation here.

[Catramen]

Clang implementation is here: (section Detailed Description)
https://clang.llvm.org/doxygen/structclang_1_1CodeGen_1_1CGBitFieldInfo.html

[Catramen]

The following structs have different layouts
typedef struct {
uint8_t a;
uint32_t b : 15;
} S;
typedef struct {
uint8_t a;
uint16_t b : 15;
} S2;

But bindgen gives same struct.

[emilio]

I took a look at this today, will submit a fix.