MAKE_3_80_realpath = $(shell $(top_srcdir)/scripts/realpath.sh '$(subst $(SQUOTE),\\$(SQUOTE),$(1))')
以上Makefile思考好几天不得要领：
今天想通了，是为记。
include $(top_srcdir)/include/mk/functions.mk
functions.mk的内容如下:
SQUOTE := '
# ' # to keep colorized editors from going nuts
MAKE_3_80_realpath = $(shell $(top_srcdir)/scripts/realpath.sh '$(subst $(SQUOTE),\\$(SQUOTE),$(1))')
MAKE_3_80_abspath = $(shell $(top_srcdir)/scripts/abspath.sh '$(subst $(SQUOTE),\\$(SQUOTE),$(1))')
几个要点：
1.'不能单独出现，所以巧妙匹配# '
2.$(1)百思不得其解，后来在source insight中搜索对MAKE_3_80_realpath 的引用 发现：
abs_top_builddir := $(call MAKE_3_80_abspath,$(top_builddir))
$(1)是call函数中的参数
'$(subst $(SQUOTE),\\$(SQUOTE),$(1))'先对参数进行字符替换，里面有个小trick，‘替换为\'
\\第一个为转移字符
$(top_srcdir)/scripts/realpath.sh
############## realpath.sh ############
. "${0%/*}/lib/file_functions.sh"
######### file_functions.sh ###########
_abspath() {
echo "$@" | awk -v PWD=$(pwd) '{
sub(/^[[:space:]]+/, ""); sub(/[[:space:]]+$/, ""); # 1.
if ($0 == "") {
print PWD
} else {
if (!($0 ~ /^\//)) { # i.
$0 = PWD "/" $0
}
while (gsub(/\/\//, "/")) { }; # ii.
while (sub(/\/[^\/]+\/\.\.\/?/, "/")) { }; # iii.
while (sub(/\/\.\//, "/")) { }; # iv.
sub(/(\/\.)?\/$/, "");
sub(/^\.\//, "/");
sub(/\/\.$/, "");
if ($0 == "") {
print "/"
} else {
if ($0 == ".") {
print PWD
} else {
print
}
}
}
}'
}
_realpath() {
readlink -f "$@"
}
######### end of file_functions.sh ####
while [ $# -gt 0 ] ; do
echo -n $(_realpath "$1")
[ $# -gt 1 ] && echo -n " "
shift
done
######### end of realpath.sh ##########
MAKE_3_80_realpath = $(shell $(top_srcdir)/scripts/realpath.sh '$(subst $(SQUOTE),\\$(SQUOTE),$(1))')
MAKE_3_80_abspath = $(shell $(top_srcdir)/scripts/abspath.sh '$(subst $(SQUOTE),\\$(SQUOTE),$(1))')
_abspath 不想去细究了，直接试一下
ttt -> safe_rm.sh
./abspath.sh ttt
/home/zhangyi/work/ltp-ddt-fmsh-psoc-test/scripts/ttt
./realpath.sh ttt
/home/zhangyi/work/ltp-ddt-fmsh-psoc-test/scripts/safe_rm.sh