Wednesday, October 16, 2013

GCC 4.8 on Ubuntu 12.04 x64

Ran into a bug in libstdc++ 4.7 building LLDB with Clang 3.3. So these are the notes on getting GCC 4.8 installed.

Here is a link talking about the libstdc++ bug:

Good askubuntu link:

Ubuntu Toolchain PPA:


sudo add-apt-repository ppa:ubuntu-toolchain-r/test

If that doesn't work, you can create the file manually:

mikesart@mikesart64:~/data/src/blah/build64$ cat /etc/apt/sources.list.d/toolchain.list
deb precise main   
deb-src precise main

sudo apt-key adv --keyserver --recv-keys 1E9377A2BA9EF27F
sudo apt-get update
sudo apt-get install gcc-4.8 g++-4.8

I then added gcc 4.8 to my alternatives list.

sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.8 50
sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.8 50
sudo update-alternatives --install /usr/bin/cpp cpp-bin /usr/bin/cpp-4.8 50

Here are some clang / gcc commands to view various options, include paths, etc.

# Show default options and commands, plus include paths
mikesart@mikesart64:~/data/src/llvm.svn/build$ clang -v -fsyntax-only -x c++ /dev/null 2>&1
clang version 3.3 (tags/RELEASE_33/final)
Target: x86_64-unknown-linux-gnu
Thread model: posix
 "/home/mikesart/data/src/clang3.3/bin/clang" -cc1 -triple x86_64-unknown-linux-gnu -fsyntax-only -disable-free -disable-llvm-verifier -main-file-name null -mrelocation-model static -mdisable-fp-elim -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -target-linker-version 2.20.1 -v -resource-dir /home/mikesart/data/src/clang3.3/bin/../lib/clang/3.3 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/x86_64-linux-gnu -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/backward -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/x86_64-linux-gnu/c++/4.8 -internal-isystem /usr/local/include -internal-isystem /home/mikesart/data/src/clang3.3/bin/../lib/clang/3.3/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -fdeprecated-macro -fdebug-compilation-dir /home/mikesart/data/src/llvm.svn/build -ferror-limit 19 -fmessage-length 181 -mstackrealign -fobjc-runtime=gcc -fobjc-default-synthesize-properties -fcxx-exceptions -fexceptions -fdiagnostics-show-option -fcolor-diagnostics -backend-option -vectorize-loops -x c++ /dev/null
clang -cc1 version 3.3 based upon LLVM 3.3 default target x86_64-unknown-linux-gnu
ignoring nonexistent directory "/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/x86_64-linux-gnu"
ignoring nonexistent directory "/include"
#include "..." search starts here:
#include <...> search starts here:
End of search list.

# Print the paths used for finding libraries and programs
mikesart@mikesart64:~/data/src/llvm.svn/build$ clang -print-search-dirs | tr : '\n'

# list all preprocessor definitions
clang -dM -E - < /dev/null
#define _LP64 1
#define __ATOMIC_ACQUIRE 2
#define __ATOMIC_ACQ_REL 4
#define __ATOMIC_CONSUME 1
#define __ATOMIC_RELAXED 0
#define __ATOMIC_RELEASE 3
#define __ATOMIC_SEQ_CST 5


Link for gcc options which control kind of output:

This one really useful: "If the -Q option appears on the command line before the --help= option, then the descriptive text displayed by --help= is changed. Instead of describing the displayed options, an indication is given as to whether the option is enabled, disabled or set to a specific value (assuming that the compiler knows this at the point where the --help= option is used)."

# See what gcc enables with native flag (sse, avx, etc)
# (Clang 3.3 doesn't appear to support the --help=XX stuff)
gcc -march=native -Q --help=target -v

--help=XX supports the following:
  optimizers: display all optimization options supported by the compiler.
  warnings: display all options controlling warning messages produced by the compiler.
  target: display target-specific options.
  params: display values recognized by the --param option.
  common: display options that are common to all languages.
  language: display options supported for language, where language = c++, etc.

You can add undocumented to list all undocumented target-specific switches as well. Ie:

/usr/bin/gcc-4.8 -march=native -Q --help=target,undocumented -v
/usr/bin/gcc-4.8 -march=native -Q --help=c++,undocumented -v

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