autoconf: Backslash-Newline-Empty

1 
1 12.4 Backslash-Newline Before Empty Lines
1 =========================================
1 
1 A bug in Bash 2.03 can cause problems if a Make rule contains a
1 backslash-newline followed by line that expands to nothing.  For
1 example, on Solaris 8:
1 
1      SHELL = /bin/bash
1      EMPTY =
1      foo:
1      	touch foo \
1      	$(EMPTY)
1 
1 executes
1 
1      /bin/bash -c 'touch foo \
1      '
1 
1 which fails with a syntax error, due to the Bash bug.  To avoid this
1 problem, avoid nullable macros in the last line of a multiline command.
1 
1    On some versions of HP-UX, `make' reads multiple newlines following
1 a backslash, continuing to the next non-empty line.  For example,
1 
1      FOO = one \
1 
1      BAR = two
1 
1      test:
1              : FOO is "$(FOO)"
1              : BAR is "$(BAR)"
1 
1 shows `FOO' equal to `one BAR = two'.  Other implementations sensibly
1 let a backslash continue only to the immediately following line.
1