Question about dead code in build-infra/common/autoconf/basics.m4

[Tim Bell]

Hello - this may be basic autoconf knowledge, but here goes:

% cat -n build-infra/common/autoconf/basics.m4
    [... snip ...]
>    162  AC_DEFUN_ONCE([BASIC_SETUP_PATHS],
>    163  [
>    164  # Where is the source? It is located two levels above the 
> configure script.
>    165  CURDIR="$PWD"
>    166  cd "$AUTOCONF_DIR/../.."
>    167  SRC_ROOT="`pwd`"
>    168  if test "x$OPENJDK_BUILD_OS" = "xwindows"; then
>    169      SRC_ROOT_LENGTH=`pwd|wc -m`
>    170      if test $SRC_ROOT_LENGTH -gt 100; then
>    171          AC_MSG_ERROR([Your base path is too long. It is 
> $SRC_ROOT_LENGTH characters long, but only 100 is supported])
>    172      fi
>    173  fi
>    174  AC_SUBST(SRC_ROOT)
>    175  cd "$CURDIR"
>    176
>    177  SPACESAFE(SRC_ROOT,[the path to the source root])
>    178  SPACESAFE(CURDIR,[the path to the current directory])
>    179  ])

Based on my experiments this evening, lines 169...172 will never be 
executed, because OPENJDK_BUILD_OS does not have a value at this point. 
The if test at line 168 evaluates to false, even on Windows build systems.


OPENJDK_BUILD_OS is defined in platform.m4, lines 358 ... 371



I see that all the .m4 files are rolled up in configure.ac, like this:

% grep m4_include configure.ac
m4_include([build-aux/pkg.m4])
m4_include([basics.m4])
m4_include([builddeps.m4])
m4_include([boot-jdk.m4])
m4_include([build-performance.m4])
m4_include([help.m4])
m4_include([jdk-options.m4])
m4_include([libraries.m4])
m4_include([platform.m4])
m4_include([source-dirs.m4])
m4_include([toolchain.m4])


Is the include order significant?  It appears to me that it is, and the 
'earlier' .m4 files can not rely on anything done in the 'later' files.

Am I missing something here?

Thanks-

Tim