I am making a ffmpeg program with cgo. I wanna statically link ffmpeg into the program.
I write these in cgo
/*
#cgo CFLAGS: -g -Wall -I./include
#cgo LDFLAGS: -L${SRCDIR}/lib -llibavformat -llibavcodec -llibavutil -llibavdevice -llibavfilter -llibswresample -llibswscale
#include "ffmpeg.h"
*/
import "C"
It builds successfully. But it will report "mssing avxxx.dll" while running. I guess it is compiled via dynamic linking.
I believe the first comment on this prior question has your answer: How to link ffmpeg statically using mingw?
Essentially, you have to have the static version of libffmpeg and -static in the CFLAGS. The bad news is that is looks like libffmpeg does not ship with static libraries so you may have to build it yourself (read the lower comments in that answer).
Related
I have a sqlite extension file. The source is sqliteext/csv.c. When I build the lib with clang the output file is created at lib/csv.so.
cc -g -fPIC -I /usr/local/include -shared sqliteext/csv.c -o lib/csv.so
When I compile the lib using zig...
zig build-lib -I /usr/local/include -I /usr/include -I /usr/include/x86_64-linux-gnu --c-source sqliteext/csv.c -dynamic --output-dir lib
There are two problems.
zig prefixes the filename with a lib
zig add a version number thing in the suffix
so the output file is lib/libcsv.so.0.0.0
And what's interesting about this is that I need to change the filename in my extension loader (that's ok) but that I also need a symlink to handle the 0.0.0.
I'm still looking at the CLI help but I'm still not seeing the thing I need.
See https://github.com/ziglang/zig/issues/2230 and https://github.com/ziglang/zig/issues/2231
The former was fixed the same day as your post via https://github.com/ziglang/zig/pull/6315
My program uses the documented autoconf macro AM_PROG_LEX. It builds fine on RHEL 6.5 and other distros, but fails on RHEL 6.6 and later.
The configure script cannot compile its tests. When it tries gcc with -ll, -lfl, linking fails with:
/usr/bin/ld: cannot find -lfl
When it tries gcc without extra libraries, linking fails with:
undefined reference to `yywrap'
libfl.a or libfl.so is missing from official repos of those systems. On RHEL 6.5 it's part of flex package.
RHEL 6.5
configure:5334: checking whether yytext is a pointer
configure:5351: gcc -o conftest -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -O0 conftest.c -lfl >&5
configure:5351: $? = 0
configure:5359: result: yes
RHEL 6.8
configure:5196: checking whether yytext is a pointer
configure:5217: gcc -o conftest -g -O2 conftest.c >&5
/tmp/ccNJtVgv.o: In function `input':
/home/git/rpmbuild/BUILD/snacc-1.3.1_16_g23ba7a6/lex.yy.c:1168: undefined reference to `yywrap'
/tmp/ccNJtVgv.o: In function `yylex':
/home/git/rpmbuild/BUILD/snacc-1.3.1_16_g23ba7a6/lex.yy.c:867: undefined reference to `yywrap'
/tmp/ccNJtVgv.o: In function `main':
/home/git/rpmbuild/BUILD/snacc-1.3.1_16_g23ba7a6/conftest.l:17: undefined reference to `yywrap'
collect2: ld returned 1 exit status
configure:5224: $? = 1
configure: failed program was:
...
configure:5246: result: no
libfl contains two and only two functions, both of which are normally unnecessary in production use of flex:
int main() { extern int yylex(void); while (yylex()) ; return 0; }
int yywrap(void) { return 1; }
The yywrap implementation (which essentially disables the yywrap functionality) is not necessary if you use the option
%option noyywrap
in your flex definition, or if you pass the command-line option --noyywrap to flex.
For quick-and-dirty flex scanners, or for debugging, it is sometimes handy to be able to use libfl to fill in the above functions. But it also can create problems on systems which provide both 32- and 64-bit environments. For this reason, libfl was removed from the RHEL flex rpm in 2014. See this RedHat bug fix advisory for details.
So you could install the appropriate flex-devel rpm in order to have libfl available. Or you could compile it yourself using the above code (which is not precisely the source code you'll find in the flex source bundle, but should produce precisely the same library).
Or you could try to fix autoconf so that it doesn't depend on libfl. It didn't used to have any such dependency; if it couldn't find libfl, it would just assume that it wasn't required for the program being compiled.
Workaround is to install flex-devel package containing libfl.a. RHEL version available to subscribers ony. Alternative is CentOS package or recompiling from source.
I'm trying to run coverage analysis on some Cython code using pytest-cov and coveralls.io. I've got as far as building the extension modules with tracing enabled, and running the analysis with the help of the links below:
http://docs.cython.org/src/tutorial/profiling_tutorial.html
http://blog.behnel.de/posts/coverage-analysis-for-cython-modules.html
However, I'm getting some results that I can't explain. It seems that many of the def/cdef/cpdef lines in the code are showing as not running, despite code within them being OK. The results aren't even consistent as some lines seem OK.
Example report: https://coveralls.io/files/1871744040
I don't know if I'm calling something wrong, if this is a bug, or if I'm just not interpreting the results correctly.
In the example above, the get_cost method seems OK, but the __set__ method for the property above is not called, despite the lines within the function having been called.
Update: It seems the issue is with Cython classes. If the class is defined with def rather than cdef the problem goes away. I guess there isn't full support for this yet.
If the Cython tracing facility does not seem to work as intended, it should be possible to use gcov for the coverage analysis of cython code. This way one could verify if some line of the generated C code is executed or not.
With a simple main.pyx
import mymod
def main():
mymod.test()
and mymod.pyx
def test():
return 42
and then
cython --embed main.pyx
cython mymod.pyx
gcc -O1 -fPIC -fprofile-arcs -ftest-coverage -Wall -I/usr/include/python2.7 -c -o main.o main.c
gcc main.o -fprofile-arcs -lpython2.7 -lgcov -o main
gcc -O1 -fPIC -fprofile-arcs -ftest-coverage -Wall -I/usr/include/python2.7 -c -o mymod.o mymod.c
gcc -shared mymod.o -fprofile-arcs -lgcov -lpython2.7 -o mymod.so
an executable was created. After executing ./main main.gcda and mymod.gcda were created for gcov.
I am adding some pthreads code into my Linux application that I'm building with autotools. I was getting an error about not linking in libpthreads. So I want to specify the pthreads dependency and compiler/linker flags in autotools.
I found some references that say use an ACX_PTHREAD macro. GNU provides an AX_PTHREAD macro. Both are very similar in concept. But I've tried both (on Ubuntu 13.04 64-bit), and found that they set -pthread in $PTHREAD_CFLAGS, but for some reason they don't set the -lpthread linker flag in $PTHREAD_LIBS.
The build fails. When I run make, I get:
...
/bin/sh ../libtool --tag=CXX --mode=link g++ -g -O2 -o myapp main.o ... -lconfuse -llog4cpp -lnsl -lpopt -lfuse -L/usr/local/lib -lrt
libtool: link: g++ -g -O2 -o .libs/myapp main.o ... -lconfuse -llog4cpp -lnsl /usr/lib/x86_64-linux-gnu/libpopt.so -lfuse -L/usr/local/lib -lrt
/usr/bin/ld: app-fuse.o: undefined reference to symbol 'pthread_kill##GLIBC_2.2.5'
/usr/bin/ld: note: 'pthread_kill##GLIBC_2.2.5' is defined in DSO /lib/x86_64-linux-gnu/libpthread.so.0 so try adding it to the linker command line
/lib/x86_64-linux-gnu/libpthread.so.0: could not read symbols: Invalid operation
collect2: error: ld returned 1 exit status
...
In this case, the ./configure step shows:
...
checking for the pthreads library -lpthreads... no
checking whether pthreads work without any flags... no
checking whether pthreads work with -Kthread... no
checking whether pthreads work with -kthread... no
checking for the pthreads library -llthread... no
checking whether pthreads work with -pthread... yes
checking for joinable pthread attribute... PTHREAD_CREATE_JOINABLE
checking if more special flags are required for pthreads... no
checking for PTHREAD_PRIO_INHERIT... yes
...
I notice it checks for -lpthreads, but shouldn't it be checking for -lpthread?
I've found that I can use:
AC_CHECK_LIB(pthread, pthread_create, [PTHREAD_LIBS+=-lpthread])
and then the build succeeds. But I assume this isn't the best way to make it work on the widest variety of platforms.
I see Ubuntu also has a package libpthread-stubs0-dev. But I'm not sure what it's for.
What is the "right way" to use pthreads with autotools?
Thanks to Peter Simons who asked on the autoconf mailing list, we have a somewhat official answer:
Compiler flags and linker flags are not mutually-exclusive sets, not
least because linking is typically done via the compiler frontend (cc)
and not by invoking the linker (ld) directly. Any flags that you can
use in the compile step (e.g. -O2, -DFOO, -I/tmp/include) will
generally be accepted in the linking step, even if it's not applicable
then. (The reverse may not be true, e.g. -lfoo.)
Given that, it's a lot less error-prone to use PTHREAD_CFLAGS (and
other CFLAGS variables) when linking, rather than duplicating the
applicable flags into PTHREAD_LIBS/LDFLAGS/etc. variables and not
using any CFLAGS variables then.
So just use PTHREAD_CFLAGS for your linker, too.
I bumped into this same issue when I added a first C++ source to an otherwise working C project (a shared library). Adding this C++ file caused libtool to switch from linking with gcc to linking with g++. Seems that linking with gcc a '-pthread' is enough to add the dynamic dependency to libpthread, but when linking with g++, it is not.
I tried with the above patch to a local ax_pthread.m4, but this didn't help. Passing '-lpthread' to g++ would fix the issue.
Edit: for some reason, ax_pthread.m4 forces C as the test language even if the AC_LANG is set as C++. This patch makes things work for me:
--- m4/ax_pthread.m4_orig 2013-06-15 20:03:36.000000000 +0300
+++ m4/ax_pthread.m4 2013-06-15 20:03:51.000000000 +0300
## -87,7 +87,6 ##
AU_ALIAS([ACX_PTHREAD], [AX_PTHREAD])
AC_DEFUN([AX_PTHREAD], [
AC_REQUIRE([AC_CANONICAL_HOST])
-AC_LANG_PUSH([C])
ax_pthread_ok=no
# We used to check for pthread.h first, but this fails if pthread.h
## -313,5 +312,4 ##
ax_pthread_ok=no
$2
fi
-AC_LANG_POP
])dnl AX_PTHREAD
It seems that the AX_PTHREAD macro is finding the -pthread compiler flag, and using that. But it looks as though for that particular flag, it should be specified to the linker as well (it apparently does the equivalent of -lpthread in the linker). I modified the macro as follows, so that the -pthread flag is specified as a linker flag too:
diff --git a/m4/ax_pthread.m4 b/m4/ax_pthread.m4
index 6d400ed..f426654 100644
--- a/m4/ax_pthread.m4
+++ b/m4/ax_pthread.m4
## -172,6 +172,12 ## for flag in $ax_pthread_flags; do
AC_MSG_CHECKING([whether pthreads work without any flags])
;;
+ -pthread)
+ AC_MSG_CHECKING([whether pthreads work with $flag])
+ PTHREAD_CFLAGS="$flag"
+ PTHREAD_LIBS="$flag"
+ ;;
+
-*)
AC_MSG_CHECKING([whether pthreads work with $flag])
PTHREAD_CFLAGS="$flag"
I guess I should submit this to the macro authors.
Expanding on a suggestion above (https://stackoverflow.com/a/20253318/221802) with exact script, this error went away for me after updating my PKbuild.sh script with pthread args:
./bootstrap && \
CPPFLAGS=" -g3 -Wall -pthread "\
CFLAGS=" -pthread -g3 -Wall "\
LDFLAGS=" -lpthread "\
./configure --enable-maintainer-mode \
--enable-debug \
--prefix=/usr \
--mandir=/usr/share/man \
--enable-pie \
--prefix=/usr \
--enable-library \
--enable-test \
......... [and so on]
I used the advice from another post: autoconf with -pthread
Here they mentioned you could download this file:
http://svn.sleuthkit.org/repos/sleuthkit/trunk/configure.ac
Place it into your m4 directory.
Then include this in your configure.ac:
ACX_PTHREAD
Finally, add this to your Makefile.am:
bin_PROGRAMS = main
main_SOURCES = main.c
main_CFLAGS = $(PTHREAD_CFLAGS)
main_LDADD = $(PTHREAD_LIBS)
I am trying to include the path to extra libraries in my makefile, but I can't figure out how to get the compiler to use that path. so far I have:
g++ -g -Wall testing.cpp fileparameters.cpp main.cpp -o test
and I want to include the path to
/data[...]/lib
because testing.cpp includes files from that library. Also, I'm on a linux machine.
EDIT: Not a path to a library. Just to files that were included. My bad.
To specify a directory to search for (binary) libraries, you just use -L:
-L/data[...]/lib
To specify the actual library name, you use -l:
-lfoo # (links libfoo.a or libfoo.so)
To specify a directory to search for include files (different from libraries!) you use -I:
-I/data[...]/lib
So I think what you want is something like
g++ -g -Wall -I/data[...]/lib testing.cpp fileparameters.cpp main.cpp -o test
These compiler flags (amongst others) can also be found at the GNU GCC Command Options manual:
3.16 Options for Directory Search
In your MakeFile or CMakeLists.txt you can set CMAKE_CXX_FLAGS as below:
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -I/path/to/your/folder")
Alternatively you could setup environment variables.
Suppose you are using bash, then in ~/.bashrc, write
C_INCLUDE_PATH="/data/.../lib/:$C_INCLUDE_PATH" ## for C compiler
CPLUS_INCLUDE_PATH="/data/.../lib/:$CPLUS_INCLUDE_PATH" ## for Cpp compiler
export C_INCLUDE_PATH
export CPLUS_INCLUDE_PATH
and source it with source ~/.bashrc.
You should be good to go.