HI-TECH Software Forums: Sizeof yields 0 (warning)

Hello

I've struck a little problem porting some code that compiles with SDCC (ANSI C99) to C51 (ANSI C89 ?).

$ c51 -v
HI-TECH 8051 C COMPILER V8.00
running on debian etch

The mm.c test:
-----------------------
#define USB_DT_STRING 0x3

code unsigned char desc_serial_str[] = {
sizeof(desc_serial_str),
USB_DT_STRING,
'1',0,'2',0,'3',0,'4',0,'5',0,'6',0
};

main()
{
}
-----------------------
gives:
mm.c: 4: Sizeof yields 0 (warning)

This compiles and correctly fills element 0 using SDCC; I suspect this is because of variable array size handling of C99.

Examining the mm.hex file shows that element 0 is initialized to zero:
00 03 31 00 32 00 33 00 34 00 35 00 36 00

I'd really like to find a way to have the size calculated by the C51. Some of the arrays are quite large so counting the entries and hard coding the size is a source of (human) error.

I've experimented with a desc_serial_end: label inside the array initialization body and a calculated size:
desc_serial_end - desc_serial_str
(hoping the linker would resolve the size) but the compiler expects a constant and this fails (as does the use of a label anyway).

Using C allows some flexible definition of USB descriptors based on modules compiled and linked for the target device and it replaces less flexible .asm files.

I'd rather not have a script that builds the descriptors if I can avoid it (so maintainers/developers have an easy view of how the descriptors are created).

Is there a C89 (or C51 specific) solution for this ?

All the best
Harry



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