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Diff for /wikisrc/pkgsrc/gcc.mdwn between versions 1.5 and 1.6

version 1.5, 2017/11/26 15:43:57 version 1.6, 2017/12/30 01:26:56
Line 19  in a compiler within ${PREFIX}, e.g. /us Line 19  in a compiler within ${PREFIX}, e.g. /us
 compiler can then be used to compile other packages.  compiler can then be used to compile other packages.
   
 The Issue with using base system gcc is typically that it is too old,  The Issue with using base system gcc is typically that it is too old,
 such as gcc 4.5 with NetBSD 6, which cannot compile c++11.  such as gcc 4.5 with NetBSD 6, which cannot compile c++11.  Another
   example is gcc 4.8 with NetBSD 7.  While this can compile most c++11
   programs, it cannot be used for firefox or glibmm (and therefore any
   package that links against glibmm).
   
 Issues when using pkgsrc gcc are that  Issues when using pkgsrc gcc are that
   
Line 84  sound while mimimizing complexity. Line 87  sound while mimimizing complexity.
     version of gcc to be used for C programs, with an OS- and      version of gcc to be used for C programs, with an OS- and
     version--specific default.      version--specific default.
   
   - A user-settable variable PKGSRC_GXX_VERSION will declare the version of gcc to    - A user-settable variable PKGSRC_GXX_VERSION will declare the
     be used for all C++ programs, again with an OS- and      version of gcc to be used for all C++ programs, again with an OS-
     version-specific default.  It must be at least PKGSRC_GCC_VERSION.      and version-specific default.  It must be at least
       PKGSRC_GCC_VERSION.
   
   - Each of c99, c++, c++11, and c++14 will be associated with a    - Each of c99, c++, c++11, and c++14 will be associated with a
     minimum gcc version, such that almost all programs declaring that      minimum gcc version, such that almost all programs declaring that
Line 137  sound while mimimizing complexity. Line 141  sound while mimimizing complexity.
   
 ## Remaining issues  ## Remaining issues
   
 ### gcc dependencies  ### gcc dependencies introduction
   
 Because gcc can have dependencies, there could be packages built with  Because gcc can have dependencies, there could be packages built with
 the system compiler that are then later used with the chosen version.  the system compiler that are then later used with the chosen version.
Line 145  For now, we defer worrying about these p Line 149  For now, we defer worrying about these p
 will be less serious than the current situation where all c++11  will be less serious than the current situation where all c++11
 programs fail to build on NetBSD 6).  programs fail to build on NetBSD 6).
   
   \todo: Change gcc 4.8 and 4.9 to enable gcc-inplace-math by default.
   
 \todo: Analyze what build-time and install-time dependencies actually  \todo: Analyze what build-time and install-time dependencies actually
 exist.  exist.  Include old GNU/Linux in this analysis.
   
   \todo: Consider if dropping nls would help.  (On NetBSD, it seems that
   base system libraries are used, so it would not help.)
   
   ### managing gcc dependencies
   
   There are multiple paths forward.
   
   \todo Choose one.  Straw proposal is "Don't worry" and recursive
   variable for the initial implementation.
   
   #### Separate prefix
   
   Build compilers in a separate prefix, or a subprefix, so that the
   compiler and the packages needed to build it will not be used by any
   normal packages.  This completely avoids the issue of building a
   package one way in bootstrap and another not in bootstrap, at the cost
   of two builds and writing the separate-prefix code.
   
   #### Don't worry
   
   Don't worry that packages used to bootstrap the needed compiler are
   compiled with an older compiler.  Don't worry that they might be
   different depending on build order.  If we have an actual problem,
   deal with it.  This requires choosing an approach to omit compiler
   selection logic when building the compiler:
   
   ##### Mark bootstrap packages
   
   Mark packages used to build gcc as PKGSRC_GCC_BOOTSTRAP=yes.
   Conditionalize this on OPSYS if necessary.  Don't force the compiler
   if this is set.
   
 \todo: Discuss adjusting options to minimize dependencies, including  ##### Pass a recursive variable
 gcc-inplace-math and nls.  
   As above, but set PKGSRC_GCC_BOOTSTRAP=yes in the evniroment of the
   call to build the compiler, so that all dependencies inherit
   permission to skip compiler selection logic.  (Alternatively, use some
   other mechanism such as passing a make variable explicitly.)
   
 ### Differing GCC and GXX versions  ### Differing GCC and GXX versions
   
Line 159  systems with a base system compiler olde Line 201  systems with a base system compiler olde
 bootstrap the compiler.  For now, we allow them to differ and will  bootstrap the compiler.  For now, we allow them to differ and will
 permit the defaults to differ.  permit the defaults to differ.
   
   ### gcc versions and number of buildable packages
   
   A gcc version that is too old will not build a number of packages.
   Anything older than 4.8 fails for c++11.  4.8 fails on some c++11
   packages, such as firefox and glibmm.
   
   A version that is too new also fails to build packages.  Analyses
   posted to tech-pkg indicate that 5 is close to 4.9 in the number of
   packages built, and that moving to 6 causes hundreds of additional
   failures.
   
   Therefore, the current answer to "What is the best version to use" is
   5.
   
   \todo Check this with Jason Bacon.
   
 ### Default versions for various systems  ### Default versions for various systems
   
 Note that if for any particular system's set of installed packages (or  Note that if for any particular system's set of installed packages (or
Line 189  PKGSRC_GCC_VERSION to 4.8 and PKGSRC_GXX Line 247  PKGSRC_GCC_VERSION to 4.8 and PKGSRC_GXX
   
 When the base system is new enough, e.g. gcc 5, 6 or 7 it should  When the base system is new enough, e.g. gcc 5, 6 or 7 it should
 simply be used.  By "new enough", we mean that almost no programs in  simply be used.  By "new enough", we mean that almost no programs in
 pkgsrc fail to build with it, which implies that it supports (almost  pkgsrc fail to build with it (because it is too old), which implies
 all) C++14 programs.  Our current definiton of new enough is gcc 5.  that it supports (almost all) C++14 programs.  Our current definiton
   of new enough is gcc 5.
   
 ### Limited mixed versions  ### Limited mixed versions
   
Line 209  situations. Line 268  situations.
 Fortran support is currently somewhat troubled..  It seems obvious to  Fortran support is currently somewhat troubled..  It seems obvious to
 extend to PGKSRC_GFORTRAN_VERSION, and have that match  extend to PGKSRC_GFORTRAN_VERSION, and have that match
 PKGSRC_GCC_VERSION or PKGSRC_GXX_VERSION, but the Fortran situation is  PKGSRC_GCC_VERSION or PKGSRC_GXX_VERSION, but the Fortran situation is
 not worsened by the above design.  \todo Discuss.  not worsened by the above design.
   
   When building a gcc version, we get gfortran.  Perhaps, because of
   fortran, we should require a single version, vs a C and a C++ version.
   
   \todo Discuss.
   
   ### C++ programs used by C programs
   
   The choice of one version for C++ and one for C (e.g. 5, 4.8 on
   netbsd-7) breaks down if a C program links against a library that is
   written in C++ but provides a C API, because we still need the C++
   version's stdlib.
   
   \todo Define a variable for such packages to have in their buildlink3,
   which will not add c++ to USE_LANGUAGES but will force
   PKGSRC_GXX_VERSION to be used.  Or decide that this is a good reason
   to really just have one compiler version.
   
 ## Path forward  ## Path forward
   
Removed from v.1.5  
changed lines
  Added in v.1.6

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