DTB build failure due to preproccessing

[Ian Campbell]

This affects arch/powerpc/boot/dts/virtex440-ml510.dts but I think it is
actually a more general issue:

        $ make ARCH=powerpc CROSS_COMPILE=powerpc-linux- virtex440-ml510.dtb 
          CC      scripts/mod/devicetable-offsets.s
          GEN     scripts/mod/devicetable-offsets.h
          HOSTCC  scripts/mod/file2alias.o
          HOSTLD  scripts/mod/modpost
          DTC     arch/powerpc/boot/virtex440-ml510.dtb
        Error: arch/powerpc/boot/dts/virtex440-ml510.dts:374.6-7 syntax error
        FATAL ERROR: Unable to parse input tree
        make[1]: *** [arch/powerpc/boot/virtex440-ml510.dtb] Error 1
        make: *** [virtex440-ml510.dtb] Error 2
        
Line 374 is the "IDSEL 0x16..." line here:
			interrupt-map = <
				/* IRQ mapping for pci slots and ALI M1533
				 ...
				 * management core also isn't used.
				 */

				/* IDSEL 0x16 / dev=6, bus=0 / PCI slot 3 */
				0x3000 0 0 1 &xps_intc_0 3 2
				0x3000 0 0 2 &xps_intc_0 2 2
				0x3000 0 0 3 &xps_intc_0 5 2
				0x3000 0 0 4 &xps_intc_0 4 2

Which gets preprocessed into:
           interrupt-map = <
        # 375 "arch/powerpc/boot/dts/virtex440-ml510.dts"
            0x3000 0 0 1 &xps_intc_0 3 2
            0x3000 0 0 2 &xps_intc_0 2 2
            0x3000 0 0 3 &xps_intc_0 5 2
            0x3000 0 0 4 &xps_intc_0 4 2

If I manually remove the "# 375 " line then that fixes the error
(although there is then a subsequent one of the same type).

I suppose this is a bug in dtc? It appears to have at least some
awareness of these preprocessor line number comments since it manages to
report the original source line number.

Ian.