I need help it is bug or I don't understand how compilation options are working ?
I have sample main.c file and try to compile it as:
$ g++ -nostdlib -g -fno-rtti -fno-exceptions -ffreestanding -nostdinc -nostdinc++ -Wl,--build-id=none,-g,-nostdlib,-nostartfiles,-zmax-page-size=0x1000 main.c -o main
and as output I have this:
$ ls
main.c startfiles
I am trying to understand why g++ created file named "startfiles" not "main" ?
If you read the GNU ld official documentation you will see that there is no option named -nostartfiles. What you do pass for arguments to the linker with that is the options -n and -ostartfiles.
If I were you, I would check those other options you try to pass to the linker as well.
-nostartfiles is a compiler flag as far as I know, not a linker flag.
For the linker, it's the same as -n -o startfiles, which is why you're getting that output file name.
Related
My Makefile:
helloworldlib.obj: helloworldlib.cpp
g++ -Wall -o helloworldlib.obj -c helloworldlib.cpp
helloworld.obj: source.cpp
g++ -Wall -o helloworld.obj -c source.cpp
helloworld.exe: source.cpp helloworld.obj
g++ -Wall -o helloworld.exe helloworld.obj helloworldlib.obj
I'm not sure what's wrong with this, when I run mingw32-make it only executes the first g++ -Wall -o helloworldlib.obj -c helloworldlib.cpp.
As far as I know this makefile is syntactically correct, mingw just doesn't seem to be able to find the other lines.
This is how make works. If no target is provided on the command line (e.g. mingw32-make helloworld.exe), by default it builds the first target defined in the file. See for instance: https://stackoverflow.com/a/2057716/2249356.
As a quick fix, you can just move the rule for helloworld.exe to the top of the file and then make will build all.
And, I think that the last rule is supposed to read
helloworld.exe: helloworld.obj helloworldlib.obj
g++ -Wall -o helloworld.exe helloworld.obj helloworldlib.obj
rather then with the source.cpp and its object code helloworld.obj as dependencies.
I compile with the following command:
gcc -Wall -march=native -O3 -ffast-math -I/usr/local/include -I/usr/local/include -o waon main.o notes.o midi.o analyse.o fft.o hc.o snd.o -L/usr/local/lib -L/usr/local/lib -lfftw3 -L/usr/local/lib -lsndfile -lm
I now would like to compile with Emscripten. How do I convert the above gcc command into an emcc command?
The command you have described in the question is linking rather than compiling. However in general you should just be able to replace gcc with emcc and it will do the right thing. In this case you will need to replace not only this linking command but also the commands used to compile the sources to the .o files.
It would probably be a good idea to take out the -march option.
It looks like your project is using libsndfile and FFTW. You will probably need to compile these libraries yourself using emscripten. Both of them are using autotools so with a bit of luck you can compile them with emscripten simply by adding the following parameters when you run the configure script:
./configure --prefix=$HOME/emscripten-libs CC=emcc
make && make install
Then when you link your program you can specify -L$HOME/emscripten-libs/lib instead of -L/usr/local/lib.
Make research about emsdk download&setup on your computer.
Download emsdk instruction
Next interest link is :
emcc or em++ instruction
https://emscripten.org/docs/tools_reference/emcc.html
When you setup emcc in command line you can see this project (i make emcc final look based on python script runner.py etc.):
c-cpp-to-javascript
Basic and useful example's :
Pretty analog with gcc :
Args:
-lGL for openGL
-s TOTAL_MEMORY=512MB --memory-init-file 1 Memory staff
--preload-file folderWithImages/--use-preload-plugins If you use assets
-I forInclude/someheader.h
-L libraryFolder/someLib.lib
-std=c11
Simple run:
./emcc -O2 a.cpp -o a.js
or
./emcc -O2 a.cpp -o a.html
Links:
./emcc -O2 a.cpp -o a.bc
./emcc -O2 b.cpp -o b.bc
./emcc -O2 a.bc b.bc -o project.js
Or :
to get JS
emcc -s WASM=1 myAdds.a myLib.a source1.c source2.cpp -o build.js
to get html
emcc -s WASM=1 myAdds.a myLib.a source1.c source2.cpp -o build.html
Link together the bitcode files:
emcc project.bc libstuff.bc -o allproject.bc
Compile the combined bitcode to HTML
emcc allproject.bc -o final.html
Important note :
You can't take an existing .a library and convert it. You must build lib with emcc also.
I am trying to have a look at assembly code generated by g++. The normal way is -S. As I also want the corresponding source code, I am adding a -fverbose-asm. (I tried both with and without.)
I expect a .s file to be generated, but none is.
What am I doing wrong ?
Invoking: Cross G++ Compiler
arm-angstrom-linux-gnueabi-g++ -march=armv7-a -mtune=cortex-a8 -mfpu=neon -mfloat-abi=softfp -flax-vector-conversions -S -fverbose-asm -DNAMESPACE -I/usr/local/angstrom/arm/lib/gcc/arm-angstrom-linux-gnueabi/4.3.3/include -O2 -Wall -c -fmessage-length=0 -Wl,-rpath-link,/usr/local/angstrom/arm/arm-angstrom-linux-gnueabi/usr/lib,--hash-style=gnu -mthumb-interwork -mno-thumb -isystem/usr/local/angstrom/arm/arm-angstrom-linux-gnueabi/usr/include -fexpensive-optimizations -frename-registers -fomit-frame-pointer -fpermissive -fPIC -mfpu=neon -MMD -MP -MF"Src/Kernel Filters SSEI.d" -MT"Src/Kernel\ Filters\ SSEI.d" -o "Src/Kernel Filters SSEI.o" "../Src/Kernel Filters SSEI.cpp"
Your assembly output is the file Src/Kernel Filters SSEI.o
Another issue is that -MT seems used incorrectly, it causes the target of the generated dependency to be the dependency file itself, rather than the object file.
You should not have any -o option to GCC to get the .s file. You are correct in passing -fverbose-asm -S to it. You may want some optimization, e.g. -O1
I suspect that your Src/Kernel Filters SSEI.o file may contain assembly code. I also strongly recommend avoiding spaces in your source or object file name. Name it Kernel_Filters_SSEI.cpp
I'm trying to create a shared library with my gcc. It's a gcc for vxworks (thats probably the problem...).
I use the gcc as following:
./gcc -shared -B/path/to/gnutools/bin -o test.so test.c
Result:
/path/to/ld: -r and -shared may not be used together
collect2: ld returned 1 exit status
If I try the same with the linux gcc, there's no problem. So i guess the gcc for VxWorks automatically passes the -r (or -i, which is the same and results in the same) flag to the linker. Is there a way to suppress this?
Greetz
marty
PS: making it static is not really an alternative...
Try compile object file separately with -fPIC and then link:
gcc -Wall -fPIC -c -o test.o test.c
gcc -Wall -shared -o test.so test.o
Another suggestion is to use libtool (at least to figure out the correct flags).
A workaround may be to go directly with ld:
ld -shared -o test.so test.o -lc
I'm trying to compile a program using a third party library, Omnet++ in my case. Apparently "make" does not find a library, but the path it uses is correct as you can see (in the sense that I can see the library under omnet++ source tree)
pv135168:basic Bob$ opp_makemake
Creating Makefile in /Users/Bob/Code/network_sim/basic... Makefile created, running "make depend" to add dependencies... opp_makedep -Y --objdirtree -I. -f Makefile -P\$O/ -- ./*.cc
pv135168:basic Bob$ make
g++ -c -g -Wall
-fno-stack-protector -m32 -DHAVE_PCAP -DXMLPARSER=libxml
-DWITH_PARSIM -DWITH_NETBUILDER -I.
-I/Users/Bob/Code/omnetpp-4.1/include -o out/gcc-debug//txc1.o txc1.cc g++ -m32 -Wl,-rpath,/Users/Bob/Code/omnetpp-4.1/lib -Wl,-rpath,. -o out/gcc-debug//basic out/gcc-debug//txc1.o -Wl,-all_load
-L"/Users/Bob/Code/omnetpp-4.1/lib/gcc"
-L"/Users/Bob/Code/omnetpp-4.1/lib" -u _tkenv_lib -lopptkenvd
-loppenvird -lopplayoutd -u _cmdenv_lib -loppcmdenvd -loppenvird
-loppsimd -lstdc++
ld: library not found for -lopptkenvd
collect2: ld returned 1 exit status make: *** [out/gcc-debug//basic]
Error 1 pv135168:basic Bob$
It's looking in the following directories for a file called libopptkenvd.dylib or libopptkenvd.a:
/Users/Bob/Code/omnetpp-4.1/lib/gcc
/Users/Bob/Code/omnetpp-4.1/lib
Is that file in one of those directories (or in the standard directories like /usr/lib)? I don't see an indication of that in your output.