I found Ofast level opt in the doc of gcc on http://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#Optimize-Options.
But when i compile my code using this level,gcc told me not recognize this flag.
I'm using gcc 4.5.2 which is the most recently released gcc.
So which version of gcc support this level?
Tnanks.
The -Ofast flag is a new feature in GCC 4.6 -- see the list of changes here.
GCC's changelog seems to indicate that this will be available in the 4.6 release series (which does not yet have a stable release). Optionally, you could try building the development sources from their SVN repo or grabbing a pre-built snapshot from one of the mirrors.
Related
I am building GCC from source for particular target. I would like to use latest GCC 7.2 release.
When I go to official GCC FTP GCC FTP, I can find only "gcc-7.2.0" release.
But, for example, in Arch Linux repository the latest GCC package is "gcc 7.2.1+20180116-1", which is, I guess, gcc-7.2.1.
So, the question is: where to find official latest source release of particular minor version of GCC?
GCC releases with a date are development snapshots. You're not looking at an official release; it's part way between 7.2.0 and 7.3.0.
You can find snapshots tagged in subversion. The website says they're in FTP too.
I want to use latest gcc compiler, but target pc configuration only has libstdc++/libc suitable for gcc 4.8.
Is there any way to tell compiler to link against older abi?
I've managed to run my application, built with newer compiler (gcc 6), when I used -std=gnu++11 flag. It seems explicitly specifying standard version makes compiler link to maximum required version of abi.
The question is about a specific combination of versions but is relevant more generally.
I've just dist-upgraded from Kubuntu 12.04 to 14.04. Now, when I want to compile CUDA code (with CUDA 6.5), I get:
#error -- unsupported GNU version! gcc 4.9 and up are not supported!
I installed gcc-4.8 (and 4.7), and tried to use the symlinks-in-/usr/local/cuda/bin solution suggested here:
CUDA incompatible with my gcc version
but this doesn't work. What should I do?
This solution is relevant to multiple combinations of CUDA and GCC versions.
You can tell CUDA's nvcc to use a specific version of gcc. So, suppose you want gcc 4.7 for use with CUDA 6. You run:
sudo apt-get install gcc-4.7 g++-4.7
and then add the following switch to your nvcc command-line:
nvcc --compiler-bindir /usr/bin/gcc-4.7 # rest of the command line here
If you're building with CMake, add an appropriate setting before looking for CUDA to your CMakeLists.txt, e.g.:
set(CUDA_HOST_COMPILER /usr/bin/gcc-4.7) # -> ADD THIS LINE <-
find_package(CUDA)
Also, it seems clang can compile CUDA as well, maybe that's worth experimenting with (although you would have to build it appropriately).
Note: Some Linux (or other OS) distributions don't have packages for multiple versions of gcc (in the same release of the OS distribution). I would advise against trying to install a package from another release of the distribution on an older release, and consider building gcc instead. That's not entirely trivial but it is quite doable - and of course, it's your only option if you don't have root access to your machine.
Switch back to a supported config. They are listed in the getting started document for any recent CUDA distribution.
For your particular configuration you have currently listed, you might have better luck with CUDA 7 RC, which is now available to registered developers.
I had a similar issue with CUDA Toolkit 7.5 and gcc 5.2.1.
I did modify the host_config.h file in /usr/local/cuda/include/:
Just remove the lines where it check the gcc version. It did solve my problem.
Credits goes to Darren Garvey (https://groups.google.com/forum/#!topic/torch7/WaNmWZqMnzw)
Very often you will find that CUDA has had newer releases by the time you encounter this problem. For example, the original formulation of the question was about CUDA 6 and GCC 4.9; CUDA 7 supported GCC 4.9. CUDA 8 supports GCC 5.x . And so on.
I'm trying to build a binary with GCC 4.9.0 that is backwards-compatible against libstdc++. According to GCC's ABI Policy and Guidelines and Options Controlling C++ Dialect, the command line option -fabi-version should do the trick; however, no matter which version I set, I still get imports of symbols from a version newer then desired, like this:
$ objdump -T binary | grep GLIBCXX_3.4.20
00000000 DF *UND* 00000000 GLIBCXX_3.4.20 _ZSt24__throw_out_of_range_fmtPKcz
I've tried -fabi-version=1 to -fabi-version=5 (ABI version 5 corresponds to GCC 4.6, which is guaranteed to be present on the target system), but those imports keep winding up in the resulting files.
How do I fix this? Going back to an old GCC version is not an option to me for other reasons.
the command line option -fabi-version should do the trick
No, that's completely unrelated to what you want. That option affects the code generated by the compiler, it does not mean you can link to an older version of libstdc++ (which is what you would need in order to stop depending on symbols in the newer libstdc++).
You cannot link to an older libstdc++ with a new GCC. The version of libstdc++ is tightly coupled to the version of GCC, so if you want to linker to an older libstdc++ then you need to compile with an older GCC.
You cannot tell libstdc++ to not use the new symbols, the reason it depends on them is because it needs them. Use an older libstdc++.
Going back to an old GCC version is not an option to me for other reasons.
Then you're screwed.
You either need to use an older GCC, or not link dynamically to libstdc++.so.
On Red Hat Enterprise Linux or CentOS you would have the option of using a newer GCC from the Developer Toolset which avoids linking to the new libstdc++.so but that is only compatible with the system GCC, which is GCC 4.4 for RHEL6 or GCC 4.7 for RHEL7. You can't use it to be compatible with GCC 4.6.
So I just downloaded mingw-w64-bin_i686-mingw_20110410.zip from here (GCC 4.7 apparently), and discovered it had a very recent version of the GCJ compiler.
I tried using it, but apparently gcj requires ecj1.exe, which is the Eclipse compiler for Java... so, where do I find a compatible version of the binaries of ECJ and the associated Java libraries that are needed (libgcj, etc.)?
Ideally this would be found on the MinGW-w64 project page, but it doesn't seem to exist.
(I've already tried copying them from a slightly older GCC version; it doesn't work.)
The cause for an openSUSE version of the gcc is basically this:
If the configure step of the compilation of gcc did not find the ecj.jar
file, ecj1 will be missing at the time when gcj, which has just been build,
is called.
ecj.jar can be taken from ftp://sourceware.org/pub/java/ecj-4.8.jar
for example.
The two options are:
i) Put ecj.jar in $HOME/share/java/ecj.jar, reconfigure gcc with
./configure .... --with-ecj-jar=$HOME/java/ecj.jar
and recompile gcc. Future compilations with that gcc will not require
ecj1 .
ii) Put ecj.jar in $HOME/share/java/ecj.jar and create ecj1(.exe)
through a compilation like
gcj -o$HOME/bin/ecj1(.exe) --main=org.eclipse.jdt.internal.compiler.batch.GCCMain $HOME/share/java/ecj.jar
assuming that the $HOME/bin is in the PATH for subsequent calls of gcj.
The thing that is actually "broken" here the fact that gcc 4.8.* is not shipped
by default with ecj.jar at some standard place.
That is a very old version of a MinGW-w64 toolchain.
I would suggest downloading one of my builds, I've had reports of gcj working (without libgcj, which does not work on Windows), although I can't seem to find a link to the discussion I had long ago with a user. The user's case had something to do with creating a JNI interface or something, which didn't require libgcj.
My old builds can be found here for 32-bit and here for 64-bit. I checked the 4.8 release build, and it contains the gcj compiler.
Would you be opposed to downloading the source and building it? I looked over the build doc in basic and advanced build docs. I didn't see anything about the GCJ compiler or ECJ, but you'll need gcc 4.5.1 in order to build it.