Require GCC 6.2 or later to build glibc

[Joseph Myers <joseph at codesourcery dot com>]

As discussed during development for glibc 2.29, when we increased the
required minimum GCC version for building glibc to GCC 5, working
purely based on the times at which such requirements have been
increased in the past it would be appropriate for glibc 2.30 to
require GCC 6 (matching GCC 4.9 having been required for glibc 2.26).
Naming 6.2 specifically as the minimum version then means a separate
version requirement no longer needs to be specified for powerpc64le.

Thus, this patch increases the minimum to 6.2, removing the
documentation of the separate requirement for powerpc64le.  It does
not remove the powerpc64le configure test, or any __GNUC_PREREQ that
could be removed as not being in installed headers or files shared
with gnulib; I think such cleanups are best done separately.

Tested for x86_64.

2019-01-31  Joseph Myers  <joseph@codesourcery.com>

	* configure.ac (libc_cv_compiler_ok): Require GCC 6.2 or later.
	* configure: Regenerated.
	* manual/install.texi (Tools for Compilation): Update minimum GCC
	version.
	* INSTALL: Regenerated.

diff --git a/INSTALL b/INSTALL
index a24ffcc722..ddb9e9018d 100644
--- a/INSTALL
+++ b/INSTALL
@@ -459,19 +459,14 @@ build the GNU C Library:
      As of relase time, GNU 'make' 4.2.1 is the newest verified to work
      to build the GNU C Library.
 
-   * GCC 5 or newer
+   * GCC 6.2 or newer
 
-     GCC 5 or higher is required.  In general it is recommended to use
+     GCC 6.2 or higher is required.  In general it is recommended to use
      the newest version of the compiler that is known to work for
      building the GNU C Library, as newer compilers usually produce
      better code.  As of release time, GCC 8.2.1 is the newest compiler
      verified to work to build the GNU C Library.
 
-     For PowerPC 64-bits little-endian (powerpc64le), GCC 6.2 or higher
-     is required.  This compiler version is the first to provide the
-     features required for building the GNU C Library with support for
-     '_Float128'.
-
      For multi-arch support it is recommended to use a GCC which has
      been built with support for GNU indirect functions.  This ensures
      that correct debugging information is generated for functions
diff --git a/NEWS b/NEWS
index 38ffd10c09..5cf568aed9 100644
--- a/NEWS
+++ b/NEWS
@@ -17,7 +17,10 @@ Deprecated and removed features, and other changes affecting compatibility:
 
 Changes to build and runtime requirements:
 
-  [Add changes to build and runtime requirements here]
+* GCC 6.2 or later is required to build the GNU C Library.
+
+  Older GCC versions and non-GNU compilers are still supported when
+  compiling programs that use the GNU C Library.
 
 Security related changes:
 
diff --git a/configure b/configure
index 101dfddf37..2643db9fb7 100755
--- a/configure
+++ b/configure
@@ -5119,7 +5119,7 @@ int
 main ()
 {
 
-#if !defined __GNUC__ || __GNUC__ < 5
+#if !defined __GNUC__ || __GNUC__ < 6 || (__GNUC__ == 6 && __GNUC_MINOR__ < 2)
 #error insufficient compiler
 #endif
   ;
diff --git a/configure.ac b/configure.ac
index 46a74687a6..ad50e290d4 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1017,7 +1017,7 @@ AC_CHECK_PROG_VER(BISON, bison, --version,
 
 AC_CACHE_CHECK([if $CC is sufficient to build libc], libc_cv_compiler_ok, [
 AC_TRY_COMPILE([], [
-#if !defined __GNUC__ || __GNUC__ < 5
+#if !defined __GNUC__ || __GNUC__ < 6 || (__GNUC__ == 6 && __GNUC_MINOR__ < 2)
 #error insufficient compiler
 #endif],
 	       [libc_cv_compiler_ok=yes],
diff --git a/manual/install.texi b/manual/install.texi
index 2cfa38772e..a9b8b4974c 100644
--- a/manual/install.texi
+++ b/manual/install.texi
@@ -499,18 +499,14 @@ As of relase time, GNU @code{make} 4.2.1 is the newest verified to work
 to build @theglibc{}.
 
 @item
-GCC 5 or newer
+GCC 6.2 or newer
 
-GCC 5 or higher is required.  In general it is recommended to use
+GCC 6.2 or higher is required.  In general it is recommended to use
 the newest version of the compiler that is known to work for building
 @theglibc{}, as newer compilers usually produce better code.  As of
 release time, GCC 8.2.1 is the newest compiler verified to work to build
 @theglibc{}.
 
-For PowerPC 64-bits little-endian (powerpc64le), GCC 6.2 or higher is
-required.  This compiler version is the first to provide the features
-required for building @theglibc{} with support for @code{_Float128}.
-
 For multi-arch support it is recommended to use a GCC which has been built with
 support for GNU indirect functions.  This ensures that correct debugging
 information is generated for functions selected by IFUNC resolvers.  This

-- 
Joseph S. Myers
joseph@codesourcery.com