![Michael Witten](/assets/img/avatar_default.png)
Among other things, the following:
commit 31160d7fea
Date: Tue Jan 8 16:22:36 2013 -0500
perf tools: Fix GNU make v3.80 compatibility issue
attempts to aid the user by tapping into an existing error message,
as described in the commit message:
... Also fix an issue where _get_attempt was called with only
one argument. This prevented the error message from printing
the name of the variable that can be used to fix the problem.
or more precisely:
-$(if $($(1)),$(call _ge_attempt,$($(1)),$(1)),$(call _ge_attempt,$(2)))
+$(if $($(1)),$(call _ge_attempt,$($(1)),$(1)),$(call _ge_attempt,$(2),$(1)))
However, The "missing" argument was in fact missing on purpose; it's
absence is a signal that the error message should be skipped, because
the failure would be due to the default value, not any user-supplied
value. This can be seen in how `_ge_attempt' uses `gea_err' (in the
config/utilities.mak file):
_ge_attempt = $(if $(get-executable),$(get-executable),$(_gea_warn)$(call _gea_err,$(2)))
_gea_warn = $(warning The path '$(1)' is not executable.)
_gea_err = $(if $(1),$(error Please set '$(1)' appropriately))
That is, because the argument is no longer missing, the value `$(1)'
(associated with `_gea_err') always evaluates to true, thus always
triggering the error condition that is meant to be reserved for
only the case when a user explicitly supplies an invalid value.
Concretely, the result is a regression in the Makefile's configuration
of python support; rather than gracefully disable support when the
relevant executables cannot be found according to default values, the
build process halts in error as though the user explicitly supplied
the values.
This new commit simply reverts the offending one-line change.
Reported-by: Pekka Enberg <penberg@kernel.org>
Link: http://lkml.kernel.org/r/CAOJsxLHv17Ys3M7P5q25imkUxQW6LE_vABxh1N3Tt7Mv6Ho4iw@mail.gmail.com
Signed-off-by: Michael Witten <mfwitten@gmail.com>
195 lines
5.6 KiB
Makefile
195 lines
5.6 KiB
Makefile
# This allows us to work with the newline character:
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define newline
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endef
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newline := $(newline)
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# nl-escape
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#
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# Usage: escape = $(call nl-escape[,escape])
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#
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# This is used as the common way to specify
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# what should replace a newline when escaping
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# newlines; the default is a bizarre string.
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#
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nl-escape = $(if $(1),$(1),m822df3020w6a44id34bt574ctac44eb9f4n)
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# escape-nl
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#
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# Usage: escaped-text = $(call escape-nl,text[,escape])
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#
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# GNU make's $(shell ...) function converts to a
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# single space each newline character in the output
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# produced during the expansion; this may not be
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# desirable.
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#
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# The only solution is to change each newline into
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# something that won't be converted, so that the
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# information can be recovered later with
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# $(call unescape-nl...)
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#
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escape-nl = $(subst $(newline),$(call nl-escape,$(2)),$(1))
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# unescape-nl
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#
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# Usage: text = $(call unescape-nl,escaped-text[,escape])
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#
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# See escape-nl.
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#
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unescape-nl = $(subst $(call nl-escape,$(2)),$(newline),$(1))
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# shell-escape-nl
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#
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# Usage: $(shell some-command | $(call shell-escape-nl[,escape]))
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#
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# Use this to escape newlines from within a shell call;
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# the default escape is a bizarre string.
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#
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# NOTE: The escape is used directly as a string constant
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# in an `awk' program that is delimited by shell
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# single-quotes, so be wary of the characters
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# that are chosen.
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#
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define shell-escape-nl
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awk 'NR==1 {t=$$0} NR>1 {t=t "$(nl-escape)" $$0} END {printf t}'
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endef
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# shell-unescape-nl
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#
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# Usage: $(shell some-command | $(call shell-unescape-nl[,escape]))
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#
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# Use this to unescape newlines from within a shell call;
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# the default escape is a bizarre string.
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#
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# NOTE: The escape is used directly as an extended regular
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# expression constant in an `awk' program that is
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# delimited by shell single-quotes, so be wary
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# of the characters that are chosen.
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#
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# (The bash shell has a bug where `{gsub(...),...}' is
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# misinterpreted as a brace expansion; this can be
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# overcome by putting a space between `{' and `gsub').
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#
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define shell-unescape-nl
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awk 'NR==1 {t=$$0} NR>1 {t=t "\n" $$0} END { gsub(/$(nl-escape)/,"\n",t); printf t }'
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endef
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# escape-for-shell-sq
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#
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# Usage: embeddable-text = $(call escape-for-shell-sq,text)
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#
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# This function produces text that is suitable for
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# embedding in a shell string that is delimited by
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# single-quotes.
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#
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escape-for-shell-sq = $(subst ','\'',$(1))
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# shell-sq
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#
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# Usage: single-quoted-and-escaped-text = $(call shell-sq,text)
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#
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shell-sq = '$(escape-for-shell-sq)'
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# shell-wordify
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#
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# Usage: wordified-text = $(call shell-wordify,text)
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#
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# For instance:
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#
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# |define text
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# |hello
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# |world
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# |endef
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# |
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# |target:
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# | echo $(call shell-wordify,$(text))
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#
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# At least GNU make gets confused by expanding a newline
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# within the context of a command line of a makefile rule
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# (this is in constrast to a `$(shell ...)' function call,
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# which can handle it just fine).
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#
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# This function avoids the problem by producing a string
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# that works as a shell word, regardless of whether or
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# not it contains a newline.
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#
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# If the text to be wordified contains a newline, then
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# an intrictate shell command substitution is constructed
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# to render the text as a single line; when the shell
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# processes the resulting escaped text, it transforms
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# it into the original unescaped text.
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#
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# If the text does not contain a newline, then this function
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# produces the same results as the `$(shell-sq)' function.
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#
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shell-wordify = $(if $(findstring $(newline),$(1)),$(_sw-esc-nl),$(shell-sq))
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define _sw-esc-nl
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"$$(echo $(call escape-nl,$(shell-sq),$(2)) | $(call shell-unescape-nl,$(2)))"
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endef
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# is-absolute
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#
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# Usage: bool-value = $(call is-absolute,path)
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#
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is-absolute = $(shell echo $(shell-sq) | grep ^/ -q && echo y)
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# lookup
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#
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# Usage: absolute-executable-path-or-empty = $(call lookup,path)
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#
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# (It's necessary to use `sh -c' because GNU make messes up by
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# trying too hard and getting things wrong).
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#
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lookup = $(call unescape-nl,$(shell sh -c $(_l-sh)))
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_l-sh = $(call shell-sq,command -v $(shell-sq) | $(call shell-escape-nl,))
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# is-executable
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#
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# Usage: bool-value = $(call is-executable,path)
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#
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# (It's necessary to use `sh -c' because GNU make messes up by
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# trying too hard and getting things wrong).
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#
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is-executable = $(call _is-executable-helper,$(shell-sq))
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_is-executable-helper = $(shell sh -c $(_is-executable-sh))
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_is-executable-sh = $(call shell-sq,test -f $(1) -a -x $(1) && echo y)
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# get-executable
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#
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# Usage: absolute-executable-path-or-empty = $(call get-executable,path)
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#
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# The goal is to get an absolute path for an executable;
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# the `command -v' is defined by POSIX, but it's not
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# necessarily very portable, so it's only used if
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# relative path resolution is requested, as determined
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# by the presence of a leading `/'.
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#
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get-executable = $(if $(1),$(if $(is-absolute),$(_ge-abspath),$(lookup)))
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_ge-abspath = $(if $(is-executable),$(1))
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# get-supplied-or-default-executable
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#
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# Usage: absolute-executable-path-or-empty = $(call get-executable-or-default,variable,default)
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#
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define get-executable-or-default
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$(if $($(1)),$(call _ge_attempt,$($(1)),$(1)),$(call _ge_attempt,$(2)))
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endef
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_ge_attempt = $(if $(get-executable),$(get-executable),$(_gea_warn)$(call _gea_err,$(2)))
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_gea_warn = $(warning The path '$(1)' is not executable.)
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_gea_err = $(if $(1),$(error Please set '$(1)' appropriately))
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# try-cc
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# Usage: option = $(call try-cc, source-to-build, cc-options, msg)
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ifneq ($(V),1)
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TRY_CC_OUTPUT= > /dev/null 2>&1
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endif
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TRY_CC_MSG=echo " CHK $(3)" 1>&2;
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try-cc = $(shell sh -c \
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'TMP="$(OUTPUT)$(TMPOUT).$$$$"; \
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$(TRY_CC_MSG) \
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echo "$(1)" | \
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$(CC) -x c - $(2) -o "$$TMP" $(TRY_CC_OUTPUT) && echo y; \
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rm -f "$$TMP"')
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