Patchwork Require GCC 6.2 or later to build glibc

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Submitter Joseph Myers
Date Jan. 31, 2019, 8:46 p.m.
Message ID <alpine.DEB.2.21.1901312045560.1258@digraph.polyomino.org.uk>
Download mbox | patch
Permalink /patch/31265/
State New
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Comments

Joseph Myers - Jan. 31, 2019, 8:46 p.m.
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.
Florian Weimer - Jan. 31, 2019, 9:28 p.m.
* Joseph Myers:

> 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.

Agreed.

> 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.

Patch looks okay to me, thanks.

Florian
Gabriel F. T. Gomes - Feb. 1, 2019, 12:03 p.m.
On Thu, Jan 31 2019, Joseph Myers wrote:
> 
> 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.

I'd like to keep the tests for powerpc64le requirements, namely, the
checks for the presence of quad-precision builtins, and POWER8 as target
(sysdeps/powerpc/powerpc64/le/configure.ac).  Was it your intention to
suggest that we should remove the check for the builtins or are these
cleanups about __GNUC_PREREQ alone?

The patch looks good to me.
Joseph Myers - Feb. 1, 2019, 4:31 p.m.
On Fri, 1 Feb 2019, Gabriel F. T. Gomes wrote:

> On Thu, Jan 31 2019, Joseph Myers wrote:
> > 
> > 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.
> 
> I'd like to keep the tests for powerpc64le requirements, namely, the
> checks for the presence of quad-precision builtins, and POWER8 as target
> (sysdeps/powerpc/powerpc64/le/configure.ac).  Was it your intention to
> suggest that we should remove the check for the builtins or are these
> cleanups about __GNUC_PREREQ alone?

I'd suggest removing the libc_cv_compiler_powerpc64le_binary128_ok 
configure test, as well as __GNUC_PREREQ calls, since the minimum GCC 
version should imply those built-in functions are available.  I think the 
point of such configure tests (for conditions that, if not met, would 
result in a build failure anyway) is to ensure a helpful early error 
saying what the problem is in the most likely cases of something wrong 
with the build tools (such as GCC being too old) - not to cover every 
theoretically possible form of compiler breakage (such as a 6.2 compiler 
somehow having had support for those built-in functions removed).

Patch

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