URL:
<http://savannah.gnu.org/bugs/?27714>
Summary: expansion of $(shell) in target forces
serialization of targets
Project: make
Submitted by: vapier
Submitted on: Fri 16 Oct 2009 07:50:48 AM GMT
Severity: 3 - Normal
Item Group: Bug
Status: None
Privacy: Public
Assigned to: None
Open/Closed: Open
Discussion Lock: Any
Component Version: 3.81
Operating System: POSIX-Based
Fixed Release: None
Triage Status: None
_______________________________________________________
Details:
i noticed a package recently that would build serially even when i gave it -j
(on a quad machine). looking into it, the reason was that $(shell) was
appended to a compiler flag leading to it being expanded when the target was
run:
CFLAGS += $(shell .....)
forcing the $(shell) to be evaluated immediately allowed things to build in
parallel:
SOME_CHECK := $(shell .....)
CFLAGS += $(SOME_CHECK)
behavior is seen with make-3.80 and make-3.81
here is a simple example:
$ cat makefile
t = 0 a b c 1 d e f 2 g h i 3 j k l 4 m n o 5 p q r 6
all: $(t)
@echo
$(t):
@printf $@ $(shell :)
$ while make -f makefile -j ; do : ; done
0abc1de2ghi3jkl4mno5pqr6
0abc1de2ghi3jkl4mno5pqr6
0abc1de2ghi3jkl4mno5pqr6
0abc1de2ghi3jkl4mno5pqr6
0abc1de2ghi3jkl4mno5pqr6
0abc1de2ghi3jkl4mno5pqr6
0abc1de2ghi3jkl4mno5pqr6
0abc1de2ghi3jkl4mno5pqr6
0abc1de2ghi3jkl4mno5pqr6
0abc1de2ghi3jkl4mno5pqr6
0abc1de2ghi3jkl4mno5pqr6
removing the $(shell :) allows for parallel evaluation:
0abc1de2gi3hjkl4mnoqr56p
0abc1de2ghi3jkl4mn5pqor6
0acde21gbhi3jkl4mno5pqr6
0abc1de2ghi3jkl4mn5qr6po
0abc1d2gehi3jkl4o5mpnqr6
0abc1de2ghi3jkl4mno5pq6r
0abc1de2ghi3jkl4mno5pqr6
0abc1de2ghi3jl4n5pkqorm6
0abc1de2ghi3jkl4mno5pqr6
0abc1de2ghi3jkl4mnpqor56
_______________________________________________________
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