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 and . --- 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 @@ -3192,6 +3192,58 @@ determine_block_size (tree len, rtx len_ 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 . */ + 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; +} + /* Helper function to do the actual work for expand_builtin_memcpy. */ static rtx @@ -3207,6 +3243,13 @@ expand_builtin_memcpy_args (tree dest, t 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 + . */ + 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 @@ -769,6 +769,8 @@ var_decl_component_p (tree var) return SSA_VAR_P (inner); } +extern bool store_reference_p (tree); + /* Fold function call to builtin mem{{,p}cpy,move}. Return false if no simplification can be made. If ENDP is 0, return DEST (like memcpy). @@ -1099,6 +1101,9 @@ gimple_fold_builtin_memory_op (gimple_st if (!srctype) return false; + if (store_reference_p (src)) + return false; + src_align = get_pointer_alignment (src); dest_align = get_pointer_alignment (dest); if (dest_align < TYPE_ALIGN (desttype) r> 2023-02-02.dir-locals.el: Add indentation rule for computed-file....Maxim Cournoyer 2022-09-07.dir-locals.el: Update yas snippets directory....Andrew Tropin 2022-09-05.dir-locals.el: Add .go to completion-ignored-extensions....Andrew Tropin 2022-09-05.dir-locals.el: Add guix yasnippets....Andrew Tropin 2022-07-10monads: Add 'mparameterize'....Ludovic Courtès 2022-07-10.dir-locals.el: Restore Emacs 27 lisp-fill-paragraph behavior....Maxim Cournoyer 2022-06-28.dir-locals.el: Properly indent 'wrap-script'....Maxim Cournoyer 2022-06-07.dir-locals: Adjust to bug-reference-mode in Emacs 28....Ludovic Courtès 2022-03-06import: github: Reuse HTTP connection for the /tags URL fallback....Ludovic Courtès 2022-03-06tests: Add (guix http-client) tests....Ludovic Courtès 2022-01-29.dir-locals.el: Don't mess up indentation of prepend and append....Liliana Marie Prikler