Building libc6 compat

Building libc6-compat

The instructions provided below specify the steps to build libc6-compat version 1.1.19 on Linux on IBM Z for the following distributions:

• RHEL (7.3, 7.4)
• SLES (12 SP2, 12 SP3)
• Ubuntu (16.04, 17.10, 18.04)

General Notes:

• When following the steps below please use a standard permission user unless otherwise specified

• A directory /<source_root>/ will be referred to in these instructions, this is a temporary writable directory anywhere you'd like to place it

Step 1: Install the Dependencies

• RHEL (7.3, 7.4)

    sudo yum install -y gcc gcc-c++ make wget tar      
  

• SLES (12 SP2, 12 SP3)

    sudo zypper install -y gcc gcc-c++ make wget tar bzip2 zlib-devel 
  

• Ubuntu (16.04, 17.10, 18.04)

    sudo apt-get update
    sudo apt-get install -y gcc g++ tar wget make cmake bzip2 zlib1g-dev g++-multilib
  

Step 2: Build and install libc6-compat

• Download source code

  cd /<source_root>/
  wget http://git.musl-libc.org/cgit/musl/snapshot/musl-1.1.19.tar.gz
  tar -xvf musl-1.1.19.tar.gz
  

• Build and install gcc 6.3.0 (Only for Ubuntu 16.04, 17.10, 18.04)

  • Get gcc source code

    cd /<source_root>/
    wget ftp://gcc.gnu.org/pub/gcc/releases/gcc-6.3.0/gcc-6.3.0.tar.gz
    tar -xvzf gcc-6.3.0.tar.gz  
    cd gcc-6.3.0/  
    ./contrib/download_prerequisites
    
    cd /<source_root>/
    mkdir gcc_build  
    cd gcc_build/  
    ../gcc-6.3.0/configure --prefix="/opt/gcc" --enable-shared --with-system-zlib --enable-threads=posix --enable-__cxa_atexit --enable-checking --enable-gnu-indirect-function --enable-languages="c,c++" --disable-bootstrap --disable-multilib  
    

    Note: By changing the prefix, you can specify a different installation directory. Make sure to use the same directory in below commands

    Note: Modify //gcc-6.3.0/gcc/ubsan.c file as per below patch only on Ubuntu 17.10 and 18.04 before building:

    --- a/gcc/ubsan.c
    +++ b/gcc/ubsan.c
    @@ -1471,7 +1471,7 @@ ubsan_use_new_style_p (location_t loc)
    
       expanded_location xloc = expand_location (loc);
       if (xloc.file == NULL || strncmp (xloc.file, "\1", 2) == 0
    -      || xloc.file == '\0' || xloc.file[0] == '\xff'
    +      || xloc.file[0] == '\0' || xloc.file[0] == '\xff'
           || xloc.file[1] == '\xff')
         return false;

  • Build and Install

    make  
    sudo make install  
    export PATH=/opt/gcc/bin:$PATH
    

• Build and Install libc6-compat

  cd /<source_root>/musl-1.1.19
  ./configure 
  make 
  sudo make install
  

Note: By default, configure installs to a prefix of "/usr/local/musl". This differs from the behavior of most configure scripts, and is chosen specifically to avoid clashing with libraries already present on the system. DO NOT set the prefix to "/usr", "/usr/local", or "/" unless you're upgrading libc on an existing musl-based system. Doing so will break your existing system when you run "make install" and it may be difficult to recover.

Step 3: Verify libc6-compat (Optional)

• After installing, you should be able to use musl via the musl-gcc wrapper. For example:

#include <stdio.h>
int main()
{
	printf("hello, world!\n");
	return 0;
}
EOF
/usr/local/musl/bin/musl-gcc hello.c
./a.out

Note: The above program should compile and execute successfully printing the string hello, world.

Notes:

• To configure autoconf-based program to compile and link against musl, set the CC variable to musl-gcc when running configure, as in: CC=musl-gcc ./configure ...
• You will probably also want to use --prefix when building libraries to ensure that they are installed under the musl prefix and not in the main host system library directories.

References:

• https://pkgs.alpinelinux.org/package/edge/main/s390x/libc6-compat
• http://www.musl-libc.org/
• http://git.musl-libc.org/cgit/musl/tree/INSTALL#n161