My C code contains #ifdef FOO. Can add something to the SCons command line to set the define, without having to modify the SConstruct/SConscript files?
I know there is a construction variable CFLAGS, and if I could get -DFOO into it, that should work. But, I cannot find a way to set construction variables from the command line.
No, unless your SConstructs/SConscripts support some sort of option/variable that you could give on the command-line (see chap. 10 "Controlling a Build From the Command-Line" in the UserGuide http://www.scons.org/doc/production/HTML/scons-user.html ).
By design, SCons uses "clean" Environments (no shell variables are imported) to protect your builds and make them repeatable. You can't simply override this by suddenly injecting flags and options from the outside.
But you can, in the SConstructs, create your build Environment such that you allow it to "import" certain shell settings (or the whole os.environ). See also #1 of the "most frequently asked FAQ" at https://bitbucket.org/scons/scons/wiki/FrequentlyAskedQuestions#markdown-header-why-doesnt-scons-find-my-compilerlinkeretc-i-can-execute-it-just-fine-from-the-command-line .
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I have a make project creating binaries using various back-ends…
→ C, C++, csharp, java… on linux using mono csharp compiler, gcc, etc…
if I choose a single back-end (example csharp) by open a XXX.cs file than the make-output-error parser working OK… this mean error-output is parsed proper and I can jump to the error right away…
if I choose the toplevel make… (open vim without file on a toplevel directory) than the make-output-error parser does not work properly.
I discovered that the vim errorformat variable has changed between 1. and 2.
and now my question: how I can tell vim to recognize the error-output from C,C++,CSharp… and Java during run of the toplevel make ?
Whatever filetype plugin you have for C# is probably changing the value of :help 'errorformat' to work with C# compilers while you are left with the default value when running your top level make which, I assume, outputs errors as-is, without any filtering.
In order for Vim to interpret correctly the potentially mixed output of all your compilers you could:
set errorformat to a value that would work with all those formats,
or add a step to your build process that unifies every native output format into a single format that Vim can interpret without effort.
First option, find the errorformat values used by every compiler and prepend them to the default value at startup:
set errorformat^=<efm for c#>
set errorformat^=<efm for cpp>
...
Second option, I've been thinking for many years about writing a program that would do just that but never found the time to even write a README.md. If such a thing doesn't exist you will have to sed and awk your way on your own I'm afraid.
In a graphical DE, like KDE, what command can be used to add a new environment variable that can be used by any other process?
Note:
1) I'm aware of export A=B, but it only works for subsequent processes started in the same shell that executed the export, processes started else where, like a graphical application such as Chrome, won't be aware of the export.
2) I'm also aware that you can put it into ~/.bash_profile or alike, but that would need a restart/relogin for the setting to take effect.
Is there something like export but have effect for all applications and doesn't require a significant restart?
Your assumption that you need to restart after placing a variable definition (whether through an export statement or otherwise) in ~/.bash_profile, is flawed. You only need to source the file again after making modifications:
source ~/.bash_profile
or the more portable version:
. ~/.bash_profile
Either statement will (re)load any definitions in that file into your current shell. Sourcing is not the same as executing the script: it will modify the environment in the calling shell itself, not a subshell running the script.
A file like ~/.bash_profile may have many other definitions and settings in it that will mess with the shell. It is better to create a small (temporary) snippet with just the variables you want, and source that instead, as #JeremiahMegel suggests.
If you want to change the environment for a single process you run from the command line, you can set the variables on the same command line:
VAR=value /usr/bin/gedit
This will run gedit with the environment variable VAR set to value, but only for that one child process.
Unfortunately, your desktop applications are a bit more static than that. Most of the graphical applications you see in the menus are probably going to be represented by .desktop files in a folder like /usr/share/applications. These files are run in an environment that has almost none of the variables you are expecting. They rely on absolute paths, and most of the configuration is done by pointing the .desktop file to a script that performs its own setup. You can modify some of these files on an individual basis if you absolutely have to, but I would not recommend doing that. If you do insist on messing around with the graphical apps on your desktop, I would recommend making a copy of the desktop files you plan to modify in to ~/.local/share/applications, or whatever the equivalent is on your system. Those files will override anything found in /usr/share/applications and will only affect you.
Just as the title said, I don't know where does this variable locate. I just know how to change it by typing:
$ export LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libXpm.so.4
Then is it possible to change it in its file?
LD_PRELOAD is an environment variable (part of the "environment" defined by the C library and Unix conventions). That specific variable tells the dynamic linker how to behave.
It is probably not set to anything by default. If you want to give it a default value every time you log in or start up a shell, you can put that export statement in your .profile or .bashrc file (or whatever the equivalent is for your shell of choice). There's probably also a place you could set it in /etc that would apply to all logins or shells started on your system (if you need it to be set for other users too).
If you only need to set it for a specific program though, that may be overkill. Instead, you might want to write a short shell script to set the environment variable up first, then launch the program. E.G.:
#!/bin/bash
export LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libXpm.so.4
~/my_program_that_needs_a_special_library
How should I change SConstruct in order to see the details of how each file is compiled?
Currently, scons only outputs a bunch of 'compiling xxx.c ...'.
It's possible with an SConstruct file to do:
SetOption('silent')
which will suppress the output of any command. Is it possible you have one of these floating around somewhere?
Addendum:
You can also set the CCOMSTR variable to override the build message for C compiles (there's a different variable for each builder though), and there's even a (not terribly well documented) PRINT_CMD_LINE_FUNC variable which would provide a general override.
I'm trying to write a configure.ac file such that the resulting configure script searches for a library directory containing a given static library e.g. libsomething.a. How can I do this? At the moment I have it check just one location with:
AC_CHECK_FILE([/usr/local/lib/libsomething.a],[AC_SUBST(libsomething,"-L/usr/local/lib -lsomething")],[AC_SUBST(libcfitsio,'')])
But I want it to try and find it automatically. And if the library isn't in one of the default locations, I'd like configure to say that the library wasn't found and that a custom location can be specified with --use-something=path as is usually done. So I also need to then check if --use-something=path is provided. I'm pretty new at creating configure files, and the M4 documentation isn't very easy to follow, so would appreciate any help.
Thanks!
It's not the job of configure to search where libraries are installed. it should only make sure they are available to the linker. If the user installed them in a different location, he knows how to call ./configure CPPFLAGS=-I/the/location/include LDFLAGS=-L/the/location/lib so that the tools will find the library (this is explained in the --help output of configure and in the standard INSTALL file).
Also --with-package and --enable-package macros are not supposed to be used to specify paths, contrary to what many third-party macros will do. The GNU Coding Standards explicitly prohibit this usage:
Do not use a --with option to
specify the file name to use to find
certain files. That is outside the scope
of what --with options are for.
CPPFLAGS and LDFLAGS are already here to address the problem, so why redevelop and maintain another mechanism?
The best way to figure this out is to look at other autoconf macros that do something similar. Autoconf macros are an amalgam of Bourne shell script and M4 code, so they can literally solve any computable problem.
Here's a link to a macro I wrote for MySQL++ that does this: mysql++.m4.