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(ld.info)ARM

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`ld''s support for interworking between ARM and Thumb code
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   For the ARM, `ld' will generate code stubs to allow functions calls
betweem ARM and Thumb code.  These stubs only work with code that has
been compiled and assembled with the `-mthumb-interwork' command line
option.  If it is necessary to link with old ARM object files or
libraries, which have not been compiled with the -mthumb-interwork
option then the `--support-old-code' command line switch should be
given to the linker.  This will make it generate larger stub functions
which will work with non-interworking aware ARM code.  Note, however,
the linker does not support generating stubs for function calls to
non-interworking aware Thumb code.

   The `--thumb-entry' switch is a duplicate of the generic `--entry'
switch, in that it sets the program's starting address.  But it also
sets the bottom bit of the address, so that it can be branched to using
a BX instruction, and the program will start executing in Thumb mode
straight away.