From cc05f407bcf77bc5a5c74c5e237d5a5aa5194bba Mon Sep 17 00:00:00 2001 From: "Yann E. MORIN" Date: Mon, 6 Jun 2016 22:43:38 +0200 Subject: [PATCH] core/pkg-utils: add macro to escape-and-printf In some cases we need to escape make variables and pass them to printf(1). This is the case in our fs infra, where we want to shoe-horn the commands to generate the filesystems in the fakeroot script, or the devices, permissions and users tables to their respective files. We currently do so by replacing $(sep) with the literal '\n' but that's not enough. This does not protect against strings with an embedded '%' or a backslash. Add a new macro that properly escapes a string and calls printf(1), so that we get the expected output. Signed-off-by: "Yann E. MORIN" Signed-off-by: Thomas Petazzoni --- package/pkg-utils.mk | 37 +++++++++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+) diff --git a/package/pkg-utils.mk b/package/pkg-utils.mk index f88313ab53..c61b3b67c4 100644 --- a/package/pkg-utils.mk +++ b/package/pkg-utils.mk @@ -104,6 +104,43 @@ define sep endef +PERCENT = % +QUOTE = ' +# ' # Meh... syntax-highlighting + +# This macro properly escapes a command string, then prints it with printf: +# +# - first, backslash '\' are self-escaped, so that they do not escape +# the following char and so that printf properly outputs a backslash; +# +# - next, single quotes are escaped by closing an existing one, adding +# an escaped one, and re-openning a new one (see below for the reason); +# +# - then '%' signs are self-escaped so that the printf does not interpret +# them as a format specifier, in case the variable contains an actual +# printf with a format; +# +# - finally, $(sep) is replaced with the literal '\n' so that make does +# not break on the so-expanded variable, but so that the printf does +# correctly output an LF. +# +# Note: this must be escaped in this order to avoid over-escaping the +# previously escaped elements. +# +# Once everything has been escaped, it is passed between single quotes +# (that's why the single-quotes are escaped they way they are, above, +# and why the dollar sign is not escaped) to printf(1). A trailing +# newline is apended, too. +# +# Note: leading or trailing spaces are *not* stripped. +# +define PRINTF + printf '$(subst $(sep),\n,\ + $(subst $(PERCENT),$(PERCENT)$(PERCENT),\ + $(subst $(QUOTE),$(QUOTE)\$(QUOTE)$(QUOTE),\ + $(subst \,\\,$(1)))))\n' +endef + # check-deprecated-variable -- throw an error on deprecated variables # example: # $(eval $(call check-deprecated-variable,FOO_MAKE_OPT,FOO_MAKE_OPTS))