I'm am taking a course in operating systems, and we were asked to explain the syntax of a given makefile. However, I'm having trouble understanding the contents:
Obj -m += simple.o
all:
make -C/lib/modules/$(shell uname -r)/build M=$(PWD) modules
clean:
make -C/lib/modules/$(shell uname -r)/build M=$(PWD) clean
The main part I don't understand is the first line. From what I know "Obj" is a variable name "-m" is a flag "+=" is the concatenate operator "simple.o" is the object file. Even though I know the parts I don't know what this line does. I have searched extensively, but I can't find any explanation of "-m" flag. It showed up in only one list explaining that the compiler knows to ignore it, see here https://www.gnu.org/software/make/manual/html_node/Options-Summary.html. Can someone explain what this line means and does?
That is a Linux kbuild makefile for an out-of-kernel-tree module. As #MadScientist has pointed out your first line should read
obj-m += simple.o
In Linux kbuild context this means "compile and link simple.c to the module". The goal all (default goal) will build the module against the kernel version you are currently running on.
NOTE: you'll need to install the kernel development headers in order for the module build to succeed.
EDIT: inside the Linux kernel tree you'll also find the notation obj-y += X which means "compile and link X into the kernel when this kernel config has been enabled".
Related
I am trying to build FreeBSD from source to see how it works. I googled how to do it, and most of the websites explaining how to build the world tell me to run this command inside the directory of the source code:
sudo make -j1 buildworld KERNCONF=MODEDKERNEL -DNO_CLEAN
For some reason, I keep getting this error...
make: invalid option -- 'D'
make: invalid option -- 'N'
Anyone know how to fix this? The Makefile can be found here
We don't need to see the makefile, because this error is being printed by make due to an invalid command line argument which means it's never even opening the makefile before it fails.
The reason is that -D, etc. are not valid command line options to GNU make. If you run man make (or look online for the GNU make manual) you'll see that -D is not listed as a valid option.
My suspicion is that when the websites you are reading are suggesting that you run make, they mean you should run FreeBSD make, which does support a -D option: https://www.freebsd.org/cgi/man.cgi?make(1)
You are trying to run this using GNU make, which does not have that option.
I am a little bit confused on how to efficiently prepare the R package, so that it will be compatible across all needed system platforms. This is needed so that the new version of package will be accepted by CRAN. The main difficulty comes from compiling external C++ shared library, and optionally CUDA version if the compiler is available. To support this flow I've created specific Makefile, unfortunately using GNU-extensions. It works fine on Linux, OSX and when executed manually via gmake on Solaris. Relevant part is here:
# Checking whether nvcc compiler is available
NVCC_TEST = $(shell basename $(shell which nvcc 2> /dev/null)"")
ifeq ($(NVCC_TEST),nvcc)
ALL_LIBS += libcucubes_gpu.so
ALL_OBJS += $(GPU_OBJS)
ALL_FLAGS += $(GPU_FLAGS)
else
ALL_OBJS += gpu_fallback.o
endif
Turns out that, when running R CMD INSTALL (...) on Solaris, the installation fails on something like this:
make: Fatal error in reader: Makefile, line 39: Unexpected end of line seen
ERROR: compilation failed for package 'libcucubes'
As it turns out, it is caused by the fact that Solaris' version of make is executed instead of GNU-compatible gmake (I've tested it works fine), even though it is available. My question is whether there is any simple way to force usage of gmake here, for the R package build. In general I know I could use autotools to solve compatibility issues during installation, but it seems to bring too much complexity for that simple case. Any advices will be really appreciated, thanks!
If you can't get your build process to use gmake instead of Solaris's pure POSIX make, you can use this hack:
Make a dedicated directory for this hack: mkdir $HOME/make_hack
Softlink gmake asmakein that directory: ln -s /path/to/gmake $HOME/make_hack/make
Set your PATH: PATH=$HOME/make_hack:$PATH
Now, run your build process using that PATH, and it should use gmake. Hopefully it just uses make from its PATH envval and not some hardcoded full path.
Yeah, it's a hack. But it's probably a lot easier than modifying the build process to use gmake instead of make.
From Writing R Extensions:
If you really must require GNU make, declare it in the DESCRIPTION
file by
SystemRequirements: GNU make
and ensure that you use the value of environment variable MAKE (and
not just make) in your scripts.
configure scripts are the preferred solution though. BTW, in general a Makevars file is also preferred over a full Makefile.
Can you set R's C and C++ flags at compilation time when installing from R CMD INSTALL (essentially, in this particular case I want to turn off compiler optimization, but ideally there's a general solution)?
I know you can affect some options using --configure-args="...", and I rather optimistically tried --configure-args="diable-optimization", to no avail. Similarly, I could also edit $RHOME/etc/Makeconf but again this is not really the kind of solution I'm looking for (and not possible where I don't have the relevant write permission).
I define my flags through an autoconf script and with a Makevars file in the package/src directory, if this makes any difference.
Dirk - very helpful discussion (as always) and definitly pointed me in the right direction. For my specific issue, it turned out in addition to the Makevars file I had to pass arguments through to configure. I have no idea why this is the case (and reading around doesn't seem to be the norm, so maybe I've done something wrong somewhere), but if anyone else has the same problem, using a ~/.R/Makevars combined with the following arguments for configure/INSTALL worked for me.
R CMD INSTALL --configure-args="CFLAGS=-g CXXFLAGS=-g" package.tar.gz
Yes, I use a file ~/.R/Makevars for that. Also handy to set CC and CXX to different compilers when, say, switching gcc versions, or switching to llvm, or ...
I can confirm that the Makevars file is very useful (specially if you need to use "-L/my/libs" or "-I/my/includes", or others build flags).
For the build, if you want to set an option for the site/machine, you can also change variables in the Makeconf file (/path/R/install/[lib64/R/]etc/Makeconf).
However, if like me, you still have some problems to manage and use libraries later, you can also set libraries with the ldpaths file [1]. This file contains the R_LD_LIBRARY_PATH used by R. This variable is the equivalent of the well known LD_LIBRARY_PATH on unix [2].
I just added some content (just before the comment on MacOS / Darwin) to this file (/path/R/install/[lib64/R/]etc/ldpaths):
if test -n "${LD_LIBRARY_PATH}"; then
R_LD_LIBRARY_PATH="${LD_LIBRARY_PATH}:${R_LD_LIBRARY_PATH}"
fi
## This is DYLD_FALLBACK_LIBRARY_PATH on Darwin (OS X) and
Then, you will be able to manage your libraries dynamically
e.g. using "environment modules" or "lmod".
Note that you can change many other environment and R variables with all the file which are in that config/etc directory (Renviron, repositories, javaconf, Rprofile.site ...).
[1] https://support.rstudio.com/hc/en-us/community/posts/200645248-Setting-up-LD-LIBRARY-PATH-for-a-rsession
[2] http://www.tldp.org/HOWTO/Program-Library-HOWTO/shared-libraries.html
I usually work on visual c++ 2010 for creating console applications as programming problems. There is this submission which requires me to give the source for the file "Makefile" by some command in unix environment
all:
g++ program.cc -o program
since i don't use unix and have never created a "makefile". I don't know how to make this submission. I have read about a makefile which is supposed to give the directions dependencies etc for compiling the program. I am using the header files iostream string and iterator in the program. i have tried the "all:" command . The bash returns command not found.
Can someone help me with this submission? The code is ready but the only thing stopping for submitting is this "makefile". please include the shell commands as well.
You're missing newline and two tabs (yes, you read right, not spaces) after the all: line, something like this:
all:
g++ helloworld.cc -o helloworld
To invoke make, type make in the directory with the Makefile. Dependencies on system headers are usually not considered, if your code has just one file, you can safely ignore that.
How to change compiler executable name? I want to perform a "fake build" of some products which are using BJam as build system. (For example: the Boost itself) In this "fake build" I want some special command to be called instead of g++. (with all the options and environment used in real build with real gcc).
How to perform this? Are there any command line switches which already allows me to do what I need or maybe I can somehow modify *.jam files to achieve what I need?
The easiest thing might to just switch your path so gcc refers to what you want to run. Otherwise, the correct way to do it bjam is more finicky. I've never gotten it to successfully, easily work, but here's what the docs suggest:
You'll need to add command to the Jamroot of your project to configure the gcc mocking command. The simplest way is just:
using gcc : : my-gcc ;
But most likely you have another using gcc ; line somewhere in your jam rules (or site-config.jam) and you'll get a complaint about trying to reinitialize a toolset. If so, you'll need to give an explicit version to the toolset like so
using gcc : mywrapper : my-gcc ;
And to use this toolset when compiling use the command bjam toolset=gcc-mywrapper.
Good luck.