Go cross-compilation with 1.5.x - output file is overridden - go

I'm using go 1.5 and I'm cross compiling like specified here.
The problem is that when compiling the project it will override the binary the last compilation created. Moreover - I will never know which OS/ARCH the executable file that I'm running was compiled to (in any case that is not windows).
Is there a way to rename the file at compile command?

You could use the "-o" argument, like this:
GOOS=linux GOARCH=386 CGO_ENABLED=0 go build -o test/output/myapp

From the page you linked to:
-o may be used to alter the name and destination of your binary, but remember that go build takes a value that is relative to your $GOPATH/src, not your working directory, so changing directories then executing the go build command is also an option.
If you use GOOS and GOARCH in the name, you should be able to achieve what you want.

Related

Flags needed to create static binaries in golang

I was building a Docker image using scratch as base.
The following build command:
RUN go build -o /go/bin/myapp
created a binary that kept failing when executed:
standard_init_linux.go:211: exec user process caused "no such file or directory"
By trial and error I found out that I needed to build as follows:
RUN CGO_ENABLED=0 go build -o /go/bin/myapp -a -ldflags '-extldflags "-static"' .
Why are both CGO_ENABLED=0 and -ldflags '-extldflags "-static"' necessary?
Don't both options create static binaries? (i.e. binaries that will need absolutely nothing in terms of libraries from the environments they will run on?)
Just before we start, a heads up by Russ Cox's: Comment
Read this as well: Comment
Yes, I agree with Volker's comment that some systems don't really allow static binaries.
Read on: Compile packages and dependencies
-a
force rebuilding of packages that are already up-to-date.
-ldflags '[pattern=]arg list'
arguments to pass on each go tool link invocation.
Read: go tool link
-extldflags flags
Set space-separated flags to pass to the external linker.
Hence, it tries to rebuild all the packages (dependencies as well) with CGO disabled and also -static means do not link against shared libraries.
Some of the points related to static linking are explained well: Linking golang statically

Generate list files with CMake

I hope this is a simple question and I'm just missing something fundamental.
I'm trying to emulate a binary build manager for an embedded Cortex-M0 target using a CMake project. I'm having some trouble figuring out how to generate list files for each dependency of my executable target.
The current build system, when building a file called main.c passes -Wa,-alh=.\CortexM0\ARM_GCC_493\Debug/main.lst as an argument to gcc. I can't figure out how to get CMake to use the current filename without the extension to save the file.
I've looked at the get_filename_component command, but it appears only to get the filename of the output:
add_executable(TestExe main.c)
get_filename_component(curr_name TestExe NAME_WM)
message(${curr_name})
As expected, this prints TestExe instead of the hoped for main
Is there a simple variable I'm overlooking that I could put in my toolchain file's CMAKE_C_FLAGS like -Wa,-alh=${CURR_SOURCE}.lst? Or some other method that I'm not seeing?
System info:
Windows 10
Msys shell
CMake 3.7.2
arm-none-eabi-gcc v4.9.3
You can use Expansion Rules and extend CMAKE_C_COMPILE_OBJECT:
set(CMAKE_C_COMPILE_OBJECT "${CMAKE_C_COMPILE_OBJECT} -Wa,-alh=<OBJECT>.lst")
But there is unfortunately
no Expansion Rule that does give the current source file without path and extension
so you will get in the above example main.c.o.lst as an output name
Footnote: In CMake generated makefile projects, if you just need the assembly file can just do make main.s or for the pre-processed file make main.i.

Choose right library version

I have a project which uses libibverbs. I have to compile this project on a server to run it there. The server has libibverbs installed system-wide, but unfortunately it doesn't support a feature which I need.
I decided to compile and use my own version of libibverbs, which has the corresponding feature. So I compiled the library, installed it to my home directory, and updated following environment variables: PATH, LD_LIBRARY_PATH, C_INCLUDE_PATH, LIBRARY_PATH, CPLUS_INCLUDE_PATH
Now I have to compile my project. First I call configure and it fails with following error message:
conftest.c:(.text.startup+0x7): undefined reference to `ibv_open_xrc_domain'
This is the symbol, which is missing in the system-wide version, but is present in the version I installed. First entry in LIBRARY_PATH is the path to the new libibversion, so I expected it is going to be used first, but it seems that the old version is used anyway.
Compilation command which ./configure uses, contains flag -L/libibverbs/1.1.4/lib, which points to the directory with the new library version. This flag goes just after -L/usr/lib/../lib64 which point to the directory, with system-wide libibverbs
If I put -L with new version in the end of command, the conftest compiles successfully.
To be clear following fails: https://gist.github.com/planetA/a421669269b14e69026c53f56fa45b2b
And following works:
https://gist.github.com/planetA/3b0e22bf6aca3a1c67f30bfa3666d9a8
Could you help me to enforce picking the new version of the library in a way that configure catches it?
LD_LIBRARY_PATH specifies directories to be searched, before the
defaults, for a library that is to be loaded in a process at runtime.
It does not affect the directories that are searched for a library
in order to link it at buildtime.
The linker searches for libraries in the directories that are specified
with the -Ldir option in its commandline, before it searches its
default directories. Your configure script tests whether it can find a libibverbs library in the linker's search directories that defines the function
ibv_open_xrc_domain, and fails because it cannot. The value of LD_LIBRARY_PATH does
not matter to this test.
For GNU make, the -L-options it should pass to the linker
are conventionally specified in the environment variable LDFLAGS. GNU autoconf - which
generates your configure script - follows this convention. autoconf generates
the configure script from the project's configure.ac file.
So, if your want your modified package to generate a generate a configure
script such that running ./configure will in turn generate makefiles
in which -L/my/library/version/is/here is passed to the linker then
you need to modify the project's configure.ac like:
LDFLAGS="$LDFLAGS -L/my/library/version/is/here"
and you need to do this in the configure.ac before it runs the test for
the libibverbs library. After making this change you will need to reconfigure
the package by running autoreconf in the project directrory, to regenerate
the configure script.
If you don't want to change the configure.ac like this then you can achieve the same
effect by:
./configure LDFLAGS="$LDFLAGS -L/my/library/version/is/here"
or:
export LDFLAGS="$LDFLAGS -L/my/library/version/is/here"
... # in same shell or a subshell
./configure
Then until the next time you run the configure script the project's makefiles
will pass -L/my/library/version/is/here to the linker. But the next time
you run ./configure you must remember to set LDFLAGS in the same way, or
the regenerated makefiles will revert to the default behaviour.

Using local makefile for CLion instead of CMake

Is there a way to configure CLion to use a local makefile to compile code, rather than CMake? I can't seem to find the way to do it from the build options.
Update: If you are using CLion 2020.2, then it already supports Makefiles. If you are using an older version, read on.
Even though currently only CMake is supported, you can instruct CMake to call make with your custom Makefile. Edit your CMakeLists.txt adding one of these two commands:
add_custom_target
add_custom_command
When you tell CLion to run your program, it will try to find an executable with the same name of the target in the directory pointed by PROJECT_BINARY_DIR. So as long as your make generates the file where CLion expects, there will be no problem.
Here is a working example:
Tell CLion to pass its $(PROJECT_BINARY_DIR) to make
This is the sample CMakeLists.txt:
cmake_minimum_required(VERSION 2.8.4)
project(mytest)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
add_custom_target(mytest COMMAND make -C ${mytest_SOURCE_DIR}
CLION_EXE_DIR=${PROJECT_BINARY_DIR})
Tell make to generate the executable in CLion's directory
This is the sample Makefile:
all:
echo Compiling $(CLION_EXE_DIR)/$# ...
g++ mytest.cpp -o $(CLION_EXE_DIR)/mytest
That is all, you may also want to change your program's working directory so it executes as it is when you run make from inside your directory. For this edit: Run -> Edit Configurations ... -> mytest -> Working directory
While this is one of the most voted feature requests, there is one plugin available, by Victor Kropp, that adds support to makefiles:
Makefile support plugin for IntelliJ IDEA
Install
You can install directly from the official repository:
Settings > Plugins > search for makefile > Search in repositories > Install > Restart
Use
There are at least three different ways to run:
Right click on a makefile and select Run
Have the makefile open in the editor, put the cursor over one target (anywhere on the line), hit alt + enter, then select make target
Hit ctrl/cmd + shift + F10 on a target (although this one didn't work for me on a mac).
It opens a pane named Run target with the output.
Newest version has better support literally for any generated Makefiles, through the compiledb
Three steps:
install compiledb
pip install compiledb
run a dry make
compiledb -n make
(do the autogen, configure if needed)
there will be a compile_commands.json file generated
open the project and you will see CLion will load info from the json file.
If you your CLion still try to find CMakeLists.txt and cannot read compile_commands.json, try to remove the entire folder, re-download the source files, and redo step 1,2,3
Orignal post: Working with Makefiles in CLion using Compilation DB
To totally avoid using CMAKE, you can simply:
Build your project as you normally with Make through the terminal.
Change your CLion configurations, go to (in top bar) :
Run -> Edit Configurations -> yourProjectFolder
Change the Executable to the one generated with Make
Change the Working directory to the folder holding your executable (if needed)
Remove the Build task in the Before launch:Activate tool window box
And you're all set! You can now use the debug button after your manual build.
Currently, only CMake is supported by CLion. Others build systems will be added in the future, but currently, you can only use CMake.
An importer tool has been implemented to help you to use CMake.
Edit:
Source : http://blog.jetbrains.com/clion/2014/09/clion-answers-frequently-asked-questions/
I am not very familiar with CMake and could not use Mondkin's solution directly.
Here is what I came up with in my CMakeLists.txt using the latest version of CLion (1.2.4) and MinGW on Windows (I guess you will just need to replace all:
g++ mytest.cpp -o bin/mytest by make if you are not using the same setup):
cmake_minimum_required(VERSION 3.3)
project(mytest)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
add_custom_target(mytest ALL COMMAND mingw32-make WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR})
And the custom Makefile is like this (it is located at the root of my project and generates the executable in a bin directory):
all:
g++ mytest.cpp -o bin/mytest
I am able to build the executable and errors in the log window are clickable.
Hints in the IDE are quite limited through, which is a big limitation compared to pure CMake projects...

How to build full go program binary with gccgo?

I have noticed that when using go build the binary result can be in excess of 2MB; but using gccgo the binary is less than 35k.
The other issue that I noticed when using gccgo is that the produced binary isn't runnable on another linux box (missing libgo.so I believe) but the go build binary runs just fine (so I imagine its because the binary includes all that is necessary to run?); is there a way to do this with gccgo?
You have to use the -static flag:
Use the -static option to do a fully static link (the default for the gc compiler).
http://golang.org/doc/install/gccgo
You can link libgo statically, while still linking the system libraries dynamically, by using the -static-libgo option. (This applies to gccgo only).
With go 1.8 or above, if go is built with CGO_ENABLED=1 (default to 1), a native compilation links dynamically. Check this variable by running go env CGO_ENABLED.
You can switch to link statically by set the environment variable CGO_ENABLED to 0 when running go build.
CGO_ENABLED=0 go build
BTW, cross compiling uses static linkage automatically.

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