gnu: Add gcc@8.

* gnu/packages/patches/gcc-8-strmov-store-file-names.patch: New file.
* gnu/local.mk (dist_patch_DATA): Register it.
* gnu/packages/gcc.scm (gcc-8): New public variable.

gnu/local.mk

@@ -707,6 +707,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/gcc-6-cross-environment-variables.patch	\
   %D%/packages/patches/gcc-6-source-date-epoch-1.patch		\
   %D%/packages/patches/gcc-6-source-date-epoch-2.patch		\
+  %D%/packages/patches/gcc-8-strmov-store-file-names.patch	\
   %D%/packages/patches/gcr-disable-failing-tests.patch		\
   %D%/packages/patches/gcr-fix-collection-tests-to-work-with-gpg-21.patch	\
   %D%/packages/patches/gd-CVE-2018-5711.patch			\

gnu/packages/gcc.scm

@@ -6,6 +6,7 @@
 ;;; Copyright © 2015, 2016, 2017, 2018 Efraim Flashner <efraim@flashner.co.il>
 ;;; Copyright © 2016 Carlos Sánchez de La Lama <csanchezdll@gmail.com>
 ;;; Copyright © 2018 Tobias Geerinckx-Rice <me@tobias.gr>
+;;; Copyright © 2018 Marius Bakke <mbakke@fastmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -515,6 +516,20 @@ Go.  It also includes runtime support libraries for these languages.")
 for several languages, including C, C++, Objective-C, Fortran, Ada, and Go.
 It also includes runtime support libraries for these languages.")))
 
+(define-public gcc-8
+  (package
+    (inherit gcc-7)
+    (version "8.1.0")
+    (source (origin
+              (method url-fetch)
+              (uri (string-append "mirror://gnu/gcc/gcc-"
+                                  version "/gcc-" version ".tar.xz"))
+              (sha256
+               (base32
+                "0lxil8x0jjx7zbf90cy1rli650akaa6hpk8wk8s62vk2jbwnc60x"))
+              (patches (search-patches "gcc-8-strmov-store-file-names.patch"
+                                       "gcc-5.0-libvtv-runpath.patch"))))))
+
 ;; Note: When changing the default gcc version, update
 ;;       the gcc-toolchain-* definitions and the gfortran definition
 ;;       accordingly.

gnu/packages/patches/gcc-8-strmov-store-file-names.patch

@@ -0,0 +1,110 @@
+Make sure that statements such as:
+
+  strcpy (dst, "/gnu/store/…");
+
+or
+
+  static const char str[] = "/gnu/store/…";
+  …
+  strcpy (dst, str);
+
+do not result in chunked /gnu/store strings that are undetectable by
+Guix's GC and its grafting code.  See <https://bugs.gnu.org/24703>
+and <https://bugs.gnu.org/30395>.
+
+--- gcc-5.3.0/gcc/builtins.c	2016-10-18 10:50:46.080616285 +0200
++++ gcc-5.3.0/gcc/builtins.c	2016-11-09 15:26:43.693042737 +0100
+@@ -3012,6 +3012,58 @@ determine_block_size (tree len, rtx len_rtx,
+ 			  GET_MODE_MASK (GET_MODE (len_rtx)));
+ }
+ 
++extern void debug_tree (tree);
++
++/* Return true if STR contains the string "/gnu/store".  */
++
++bool
++store_reference_p (tree str)
++{
++  if (getenv ("GUIX_GCC_DEBUG") != NULL)
++    debug_tree (str);
++
++  if (TREE_CODE (str) == ADDR_EXPR)
++    str = TREE_OPERAND (str, 0);
++
++  if (TREE_CODE (str) == VAR_DECL
++      && TREE_STATIC (str)
++      && TREE_READONLY (str))
++    {
++      /* STR may be a 'static const' variable whose initial value
++         is a string constant.  See <https://bugs.gnu.org/30395>.  */
++      str = DECL_INITIAL (str);
++      if (str == NULL_TREE)
++        return false;
++    }
++
++  if (TREE_CODE (str) != STRING_CST)
++    return false;
++
++  int len;
++  const char *store;
++
++  store = getenv ("NIX_STORE") ? getenv ("NIX_STORE") : "/gnu/store";
++  len = strlen (store);
++
++  /* Size of the hash part of store file names, including leading slash and
++     trailing hyphen.  */
++  const int hash_len = 34;
++
++  if (TREE_STRING_LENGTH (str) < len + hash_len)
++    return false;
++
++  /* We cannot use 'strstr' because 'TREE_STRING_POINTER' returns a string
++     that is not necessarily NUL-terminated.  */
++
++  for (int i = 0; i < TREE_STRING_LENGTH (str) - (len + hash_len); i++)
++    {
++      if (strncmp (TREE_STRING_POINTER (str) + i, store, len) == 0)
++	return true;
++    }
++
++  return false;
++}
++
+ /* Try to verify that the sizes and lengths of the arguments to a string
+    manipulation function given by EXP are within valid bounds and that
+    the operation does not lead to buffer overflow or read past the end.
+@@ -3605,6 +3657,13 @@ expand_builtin_memory_copy_args (tree dest, tree src, tree len,
+   unsigned HOST_WIDE_INT max_size;
+   unsigned HOST_WIDE_INT probable_max_size;
+ 
++  /* Do not emit block moves, which translate to the 'movabs' instruction on
++     x86_64, when SRC refers to store items.  That way, store references
++     remain visible to the Guix GC and grafting code.  See
++     <https://bugs.gnu.org/24703>.  */
++  if (store_reference_p (src))
++    return NULL_RTX;
++
+   /* If DEST is not a pointer type, call the normal function.  */
+   if (dest_align == 0)
+     return NULL_RTX;
+--- gcc-5.5.0/gcc/gimple-fold.c	2018-03-20 11:36:16.709442004 +0100
++++ gcc-5.5.0/gcc/gimple-fold.c	2018-03-20 11:46:43.838487065 +0100
+@@ -635,6 +635,8 @@ var_decl_component_p (tree var)
+   return SSA_VAR_P (inner);
+ }
+ 
++extern bool store_reference_p (tree);
++
+ /* If the SIZE argument representing the size of an object is in a range
+    of values of which exactly one is valid (and that is zero), return
+    true, otherwise false.  */
+@@ -742,6 +744,9 @@ gimple_fold_builtin_memory_op (gimple_stmt_iterator *gsi,
+       off0 = build_int_cst (build_pointer_type_for_mode (char_type_node,
+ 							 ptr_mode, true), 0);
+ 
++      if (store_reference_p (src))
++        return false;
++
+       /* If we can perform the copy efficiently with first doing all loads
+          and then all stores inline it that way.  Currently efficiently
+ 	 means that we can load all the memory into a single integer