> last updated 04 April 2000, of `The GNU Make > Manual', for `make', Version 3.79. I use: GNU Make > version 3.79.1
(Wow, that's pretty old skool.) > It seems as if it is not possible to change the value > of a variable inside an ?ifeq? conditional that test > against that very variable That would be a strange and distressing bug, but I would guess you'll find the documentation for the actual cause of the problem if you search for "override". > The prerequisites are processed from left to right > (as one would expect) If your makefile doesn't specify an order (by making one prerequisite depend on another), then the order is deliberately undefined. This gives make the freedom to, for example, build the prerequisites in parallel. A -j switch to invoke that can often be beneficial on modern hardware. Hope that helps, albeit indirectly. ----- Original Message ----- From: [EMAIL PROTECTED] <[EMAIL PROTECTED]> To: bug-make@gnu.org <bug-make@gnu.org> Sent: Sat Oct 25 13:42:55 2008 Subject: possible bug in documentation for make <bug-make@gnu.org>. Hello, I found two problems which I think are bugs in the documentation for ?make?: 1) Limitations of redefining a variable inside a conditional are not clear. 2) The order, in which prerequisites are processed, is not clear. I refer to: Edition 0.55, last updated 04 April 2000, of `The GNU Make Manual', for `make', Version 3.79. I use: GNU Make version 3.79.1, Built for i386-pc-msdosdjgpp (not the newest version, I presume, but maybe no one mentioned the problem yet?) 1st problem: In an attempt to reduce tedious typing when defining a variable from the command line, I tried: ifeq (max,$(O)) O = -O3 -fomit-frame-pointer -fno-unroll-loops endif ifeq (,$(O)) O = -O endif CXXFLAGS = -W -Wall $(O) but this didn?t work. After typing ?make O=max? the value ?max? was passed straight to the compiler instead of being changed to ?-O3 -fomit-frame-pointer -fno-unroll-loops?. I had to use the more complex sequence ifeq (max,$(O)) OPTIM = -O3 -fomit-frame-pointer -fno-unroll-loops endif ifeq (,$(O)) OPTIM = -O endif ifndef OPTIM OPTIM = $(O) endif CXXFLAGS = -W -Wall $(OPTIM) It seems as if it is not possible to change the value of a variable inside an ?ifeq? conditional that test against that very variable, but I wasn?t told in the documentation. 2nd problem: In most cases, of course, the order of processing the prerequisites doesn?t matter, but I have to struggle with the limitations of the DOS shell ?command.com?. (Therefore several quirky ways to split long command lines in target ?sicher? of the appended makefile.) I use djgpp?s ?redir? program to create a logfile (?sml.log?), to which the various compiler, assembler and linker messages are appended successively (redir?s option -ea). So, an existing logfile, containing junk from earlier compilations, has to be removed _before_ any other action takes place. I achive this by putting the phony target ?klar? first in the prerequisite list of target ?all?. Phony target ?tst?, showing the final results of compilation, is put last, behind the real target. So far, everything works fine. The prerequisites are processed from left to right (as one would expect). However, when updating the makefile itself (target ?makefile?), the order seems to be the reverse. Command echoing (given in the appended file ?makelog.log?) shows re-generation of ?vid.d? first, followed by ?schirm.d? etc., the first prerequisite??sim.d?, coming last. Prerequisites are processed from right to left! Although this causes no problem, it?s a bit puzzling, and I can?t find anything about it in the documentation. I?d like to suggest that one or two sentences about this be added to the (otherwise very good, not to say exhaustive!) documentation. (Or maybe ?make? itself can be changed to a more consistent behaviour?) Greetings Bernhard Strowitzki ____________________________________________________________________ Psssst! Schon vom neuen WEB.DE MultiMessenger gehört? Der kann`s mit allen: http://www.produkte.web.de/messenger/?did=3123
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