Initialize union inside of struct: cannot find why Missing brace around initializer - c

Question

I am trying to initialize properly this struct:
typedef struct
{
TU_ApplicationData uApplicationData;
TS_SHA_Padding sSHA_Padding;
TU_ApplicationNonVolatileData uApplicationNonVoltatileData;
TS_SHA_Digest sSHA_Digest;
}TS_ApplicationFooter;
As you can see, it is composed with other structure:
typedef struct
{
uint32_t u32ApplicationVersion_Major;
uint32_t u32ApplicationVersion_Minor;
fpJumpHandler fpApplicationJumpHandler;
uint32_t u32BootApplicationStartAddress;
uint32_t u32BootApplicationAllocationSize;
uint32_t u32UserApplicationStartAddress;
uint32_t u32UserApplicationAllocationSize;
}TS_ApplicationData;
typedef union
{
uint32_t au32ApplicationData[32];
TS_ApplicationData sApplicationData;
}TU_ApplicationData;
typedef struct
{
uint32_t u32SHA_1PaddingBytes[16];
}TS_SHA_Padding;
typedef struct
{
uint8_t u8ApplicationNonVoltatileData[256];
}TU_ApplicationNonVolatileData;
typedef struct
{
uint32_t au32ApplicationHashTag[16];
}TS_SHA_Digest;
I cannot find the proper way to initialize the TS_ApplicationFooter structure. The best way that I have is the following, but it returns me the warning: "missing braces around initializer [-Wmissing-braces]".
const TS_ApplicationFooter sUserApplicationFooter =
{ /* Warning point here */
.uApplicationData=
{
.au32ApplicationData={0},
.sApplicationData=
{
.u32ApplicationVersion_Major=U32_USB_CDC_USER_APP_SW_RELEASE_MAJOR_VERSION,
.u32ApplicationVersion_Minor=U32_USB_CDC_USER_APP_SW_RELEASE_MINOR_VERSION,
.fpApplicationJumpHandler=NULL,
.u32BootApplicationStartAddress=U32_BOOT_LOADER_APPLICATION_START_ADDRESS,
.u32BootApplicationAllocationSize=U32_BOOT_LOADER_APPLICATION_ALLOCATED_SIZE,
.u32UserApplicationStartAddress=U32_USER_APPLICATION_START_ADDRESS,
.u32UserApplicationAllocationSize=U32_USER_APPLICATION_ALLOCATED_SIZE
}
},
.sSHA_Padding={0},
.uApplicationNonVoltatileData={0},
.sSHA_Digest={0}
};
Do you have any idea on how I could initialize this structure without having any warning of this kind ?

Answer 1

You should add extra braces around the last three members to appease GCC:
...
.sSHA_Padding={{0}},
.uApplicationNonVoltatileData={{0}},
.sSHA_Digest={{0}}
};
This might be a bug in GCC. Clang does not show this warning, even if compiled with -Wall -W -Wmissing-braces -pedantic.
Alternatively, since as soon as you initialize one member member of a struct, all other members that are not explicitly initialized are initialized to zero, you can just omit them.
Furthermore, you should only initialize exactly one member of a union! I recommend you rewrite the whole initialization like so:
const TS_ApplicationFooter sUserApplicationFooter =
{
.uApplicationData =
{
.sApplicationData =
{
.u32ApplicationVersion_Major = U32_USB_CDC_USER_APP_SW_RELEASE_MAJOR_VERSION,
.u32ApplicationVersion_Minor = U32_USB_CDC_USER_APP_SW_RELEASE_MINOR_VERSION,
.u32BootApplicationStartAddress = U32_BOOT_LOADER_APPLICATION_START_ADDRESS,
.u32BootApplicationAllocationSize = U32_BOOT_LOADER_APPLICATION_ALLOCATED_SIZE,
.u32UserApplicationStartAddress = U32_USER_APPLICATION_START_ADDRESS,
.u32UserApplicationAllocationSize = U32_USER_APPLICATION_ALLOCATED_SIZE
}
},
};