Hello.
After receiving feedback from Richi and Wilco Dijkstra, I decided to fully not
support not null-terminated strings. It brings more complications and the code
has started
to be overengineered. Thus c_getstr accepts only such strings and as a bonus it
returns
length of a string.
Patch can bootstrap on ppc64le-redhat-linux and survives regression tests.
Ready to be installed?
Martin
>From bee44f0dedc86b1c354e21dd87dad6313147dcc3 Mon Sep 17 00:00:00 2001
From: marxin
Date: Thu, 13 Oct 2016 10:20:12 +0200
Subject: [PATCH 1/4] Support only \0-terminated string in c_getstr and return
strlen
gcc/ChangeLog:
2016-10-13 Martin Liska
* fold-const.c (c_getstr): Support of properly \0-terminated
string constants. New argument is added.
* fold-const.h: New argument is added.
---
gcc/fold-const.c | 38 +-
gcc/fold-const.h | 2 +-
2 files changed, 30 insertions(+), 10 deletions(-)
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 02aa484..57a9243 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -14440,24 +14440,44 @@ fold_build_pointer_plus_hwi_loc (location_t loc, tree ptr, HOST_WIDE_INT off)
}
/* Return a char pointer for a C string if it is a string constant
- or sum of string constant and integer constant. */
+ or sum of string constant and integer constant. We only support
+ string constants properly terminated with '\0' character.
+ If STRLEN is a valid pointer, length (including terminating character)
+ of returned string is stored to the argument. */
const char *
-c_getstr (tree src)
+c_getstr (tree src, unsigned HOST_WIDE_INT *strlen)
{
tree offset_node;
+ if (strlen)
+*strlen = 0;
+
src = string_constant (src, &offset_node);
if (src == 0)
-return 0;
+return NULL;
- if (offset_node == 0)
-return TREE_STRING_POINTER (src);
- else if (!tree_fits_uhwi_p (offset_node)
- || compare_tree_int (offset_node, TREE_STRING_LENGTH (src) - 1) > 0)
-return 0;
+ unsigned HOST_WIDE_INT offset = 0;
+ if (offset_node != NULL_TREE)
+{
+ if (!tree_fits_uhwi_p (offset_node))
+ return NULL;
+ else
+ offset = tree_to_uhwi (offset_node);
+}
+
+ unsigned HOST_WIDE_INT string_length = TREE_STRING_LENGTH (src);
+ const char *string = TREE_STRING_POINTER (src);
+
+ /* Support only properly null-terminated strings. */
+ if (string_length == 0
+ || string[string_length - 1] != '\0'
+ || offset > string_length)
+return NULL;
- return TREE_STRING_POINTER (src) + tree_to_uhwi (offset_node);
+ if (strlen)
+*strlen = string_length - offset;
+ return string + offset;
}
#if CHECKING_P
diff --git a/gcc/fold-const.h b/gcc/fold-const.h
index 637e46b..bc22c88 100644
--- a/gcc/fold-const.h
+++ b/gcc/fold-const.h
@@ -182,7 +182,7 @@ extern bool expr_not_equal_to (tree t, const wide_int &);
extern tree const_unop (enum tree_code, tree, tree);
extern tree const_binop (enum tree_code, tree, tree, tree);
extern bool negate_mathfn_p (combined_fn);
-extern const char *c_getstr (tree);
+extern const char *c_getstr (tree, unsigned HOST_WIDE_INT *strlen = NULL);
/* Return OFF converted to a pointer offset type suitable as offset for
POINTER_PLUS_EXPR. Use location LOC for this conversion. */
--
2.9.2