Fill

The -fill option is used for filling unused memory locations with a known value. The usage of this option is:

-fill=[const_width:]fill_expr@address[:end_address]

where:

• const_width has the form wn and signifies the width (n bytes) of each constant in fill_expr. If const_width is not specified, the default value is two bytes. For example, -fill=w1:1 with fill every unused byte with the value 0x01.
• fill_expr can use the syntax (where const and increment are n-byte constants):
  • const fill memory with a repeating constant; i.e., -fill=0xBEEF becomes 0xBEEF, 0xBEEF, 0xBEEF, 0xBEEF.
  • const+=increment fill memory with an incrementing constant; i.e., -fill=0xBEEF+=1 becomes 0xBEEF, 0xBEF0, 0xBEF1, 0xBEF2.
  • const-=increment fill memory with a decrementing constant; i.e., -fill=0xBEEF-=0x10 becomes 0xBEEF, 0xBEDF, 0xBECF, 0xBEBF.
  • const,const,...,const fill memory with a list of repeating constants; i.e., -fill=0xDEAD,0xBEEF becomes 0xDEAD,0xBEEF,0xDEAD,0xBEEF.
• The options following fill_expr result in the following behavior:
  • @address fill a specific address with fill_expr; i.e., -fill=0xBEEF@0x1000 puts 0xBEEF at address 1000h. If the fill value is wider than the addressing value specified with -addressing, then only part of the fill value is placed in the output. For example, if the addressing is set to 1, the option above will place 0xEF at address 0x1000 and a warning will be issued.
  • @address:end_address fill a range of memory with fill_expr; i.e., -fill=0xBEEF@0:0xFF puts 0xBEEF in unused addresses between 0 and 255. If the address range (multiplied by the -ADDRESSING value) is not a multiple of the fill value width, the final location will only use part of the fill value, and a warning will be issued.

The fill values are word-aligned so they start on an address that is a multiple of the fill width. Should the fill value be an instruction opcode, this alignment ensures that the instruction can be executed correctly. Similarly, if the total length of the fill sequence is larger than 1 (and even if the specified width is 1), the fill sequence is aligned to that total length. For example the following fill option, which specifies 2 bytes of fill sequence and a starting address that is not a multiple of 2:

-fill=w1:0x11,0x22@0x11001:0x1100c

will result in the following hex record, where the starting address was filled with the second byte of the fill sequence due to this alignment.

:0C100100221122112211221122112211B1

All constants can be expressed in (unsigned) binary, octal, decimal or hexadecimal, as per normal C syntax, for example, 1234 is a decimal value, 0xFF00 is hexadecimal and FF00 is illegal.