Mapfile option defaults

The ld command has three built-in segments (text, data, and note) with default segment_attribute_values and corresponding default mapping directives as described under ``Segment declarations''. Even though the ld command does not use an actual ``mapfile'' to store the defaults, the model of a ``default mapfile'' helps to illustrate what happens when the ld command encounters your mapfile.

``Default mapfile'' shows how a mapfile would appear for the ld command defaults. The ld command begins execution behaving as if the mapfile in ``Default mapfile'' has already been read in. Then ld reads your mapfile and either augments or makes changes to the defaults.

Default mapfile

text = LOAD ?RX;
text : $PROGBITS ?A!W;

data = LOAD ?RWX;
data : $PROGBITS ?AW;
data : $NOBITS ?AW;

note = NOTE;
note : $NOTE;

1. If the segment does not already exist in the mapfile, but another with the same segment-type value exists, the segment is added before all of the existing segments of the same segment_type.

2. If none of the segments in the existing mapfile has the same segment_type value as the segment just read in, then the segment is added by segment_type value to maintain the following order:
   
   1. INTERP
   2. LOAD
   3. DYNAMIC
   4. NOTE

3. If the segment is of segment_type LOAD and you have defined a virtual_address value for this LOADable segment, the segment is placed before any LOADable segments without a defined virtual_address value or with a higher virtual_address value, but after any segments with a virtual_address value that is lower.