diff options
Diffstat (limited to 'lib/am/header-vars.am')
| -rw-r--r-- | lib/am/header-vars.am | 33 |
1 files changed, 30 insertions, 3 deletions
diff --git a/lib/am/header-vars.am b/lib/am/header-vars.am index 463531a90..9283903a1 100644 --- a/lib/am/header-vars.am +++ b/lib/am/header-vars.am @@ -27,9 +27,36 @@ VPATH = @srcdir@ ## DESTDIR = ## Shell code that determines whether we are running under GNU make. -## This is somewhat of an hack, and might be improved, but is good -## enough for now. -am__is_gnu_make = test -n '$(MAKEFILE_LIST)' && test -n '$(MAKELEVEL)' +## +## Why the this needs to be so convoluted? +## +## (1) We can't unconditionally use make functions or special variables +## starting with a dot, as those cause non-GNU implmentations to +## crash hard. +## +## (2) We can't use $(MAKE_VERSION) here, as it is also defined in some +## non-GNU make implementations (e.g., FreeBSD make). But at least +## BSD make does *not* define the $(CURDIR) variable -- it uses +## $(.CURDIR) instead. +## +## (3) We can't use $(MAKEFILE_LIST) here, as in some situations it +## might cause the shell to die with "Arg list too long" (see +## automake bug#18744). +## +## (4) We can't use $(MAKE_HOST) unconditionally, as it is only +## defined in GNU make 4.0 or later. +## +am__is_gnu_make = { \ + if test -z '$(MAKELEVEL)'; then \ + false; \ + elif test -n '$(MAKE_HOST)'; then \ + true; \ + elif test -n '$(MAKE_VERSION)' && test -n '$(CURDIR)'; then \ + true; \ + else \ + false; \ + fi; \ +} ## Shell code that determines whether the current make instance is ## running with a given one-letter option (e.g., -k, -n) that takes |