111 lines
3.3 KiB
Diff
111 lines
3.3 KiB
Diff
commit 8b89515caca5149329c0cd20485e69e2d0f879d4
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Author: Marek Polacek <polacek@redhat.com>
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Date: Wed Dec 7 13:44:38 2022 -0500
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strlen: Use D_S_U in maybe_set_strlen_range
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This patch fixes #2137448 where the customer uses strlen on a buffer
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that was filled by converting the buffer to a struct and copying a string
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into a flexible array member of the struct.
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This regressed with r262438 in the sense that the strlen was folded to 0.
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The strlen=0 result started with
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https://gcc.gnu.org/pipermail/gcc-patches/2018-July/501912.html
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https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=715fcd73b66c639d9e0e3f3ef9c6ff9d621d7131
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which seems like an undesirable change. It was fixed (back to strlen=3) by
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https://gcc.gnu.org/legacy-ml/gcc-patches/2019-01/msg00069.html
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https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=d4bf69750d31d08068f8242225b8fa06cdf11411
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but the changes are not backportable.
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Instead, this patch makes maybe_set_strlen_range use DECL_SIZE_UNIT
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rather than TYPE_SIZE_UNIT, fixing the regression.
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I could never reproduce the problem in C, only C++. C/C++ represent array
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type domains differently: C has
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char[0:]
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but C++
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char[0:18446744073709551615]
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I'm not sure if that explains it. In any case, I put the new test into
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c-c++-common/.
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Also, the original test had
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printf("strlen = %zu\n", strlen(q->name));
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so naturally, for the testsuite, I wanted to convert that into
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if (strlen(q->name) != ...)
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__builtin_abort ();
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but then I could no longer reproduce the problem. After some poking
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I realized I want -fno-early-inlining.
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Co-authored-by: Jakub Jelinek <jakub@redhat.com>
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diff --git a/gcc/testsuite/c-c++-common/torture/strlenopt-1.c b/gcc/testsuite/c-c++-common/torture/strlenopt-1.c
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new file mode 100644
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index 00000000000..e8c11044119
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--- /dev/null
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+++ b/gcc/testsuite/c-c++-common/torture/strlenopt-1.c
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@@ -0,0 +1,38 @@
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+/* { dg-do run } */
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+/* { dg-options "-fno-early-inlining" } */
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+
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+#define FORTIFY_SOURCE 2
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+
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+struct S {
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+ char skip;
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+ char name[0];
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+};
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+
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+static char static_buf[4];
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+
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+static void
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+print_name_len(void *p)
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+{
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+ struct S *q = (struct S *) p;
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+ if (__builtin_strlen(q->name) != 2)
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+ __builtin_abort ();
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+}
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+
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+int
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+main(void)
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+{
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+ // treat static storage as struct
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+ struct S *c = (struct S *)static_buf;
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+ __builtin_strcpy(c->name, "aa");
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+
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+ // copy static storage to stack storage
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+ char stack_buf[4] = { 0 };
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+ __builtin_memcpy(stack_buf, static_buf, 4);
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+
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+ // static and stack both now contain ( 0, 'a', 'a', 0 }
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+
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+ // indirectly pass the stack storage to the length function
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+ char *s = (char *)stack_buf;
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+ print_name_len(s);
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+ return 0;
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+}
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diff --git a/gcc/tree-ssa-strlen.c b/gcc/tree-ssa-strlen.c
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index 55e82e7b638..da47046cc2a 100644
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--- a/gcc/tree-ssa-strlen.c
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+++ b/gcc/tree-ssa-strlen.c
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@@ -1200,8 +1200,11 @@ maybe_set_strlen_range (tree lhs, tree src)
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|| array_at_struct_end_p (src))
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return;
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- tree type = TREE_TYPE (src);
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- if (tree size = TYPE_SIZE_UNIT (type))
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+ src = get_base_address (src);
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+ if (!DECL_P (src))
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+ return;
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+
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+ if (tree size = DECL_SIZE_UNIT (src))
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if (size && TREE_CODE (size) == INTEGER_CST)
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{
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wide_int max = wi::to_wide (size);
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