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From 7d3f53c595e1766ca0494e5f56f33b0ce49b3bb4 Mon Sep 17 00:00:00 2001
From: Martin Sebor <msebor@redhat.com>
Date: Thu, 15 Jul 2021 10:11:23 -0600
Subject: [PATCH] Avoid -Wvla-parameter for nontrivial bounds [PR97548].
Resolves:
PR c/101289 - bogus -Wvla-paramater warning when using const for vla param
PR c/97548 - bogus -Wvla-parameter on a bound expression involving a parameter
gcc/c-family/ChangeLog:
PR c/101289
PR c/97548
* c-warn.c (warn_parm_array_mismatch): Use OEP_DECL_NAME.
gcc/c/ChangeLog:
PR c/101289
PR c/97548
* c-decl.c (get_parm_array_spec): Strip nops.
gcc/ChangeLog:
PR c/101289
PR c/97548
* fold-const.c (operand_compare::operand_equal_p): Handle OEP_DECL_NAME.
(operand_compare::verify_hash_value): Same.
* tree-core.h (OEP_DECL_NAME): New.
gcc/testsuite/ChangeLog:
* gcc.dg/Wvla-parameter-12.c: New test.
---
gcc/c-family/c-warn.c | 3 +-
gcc/c/c-decl.c | 1 +
gcc/fold-const.c | 33 ++++++++++++++++------
gcc/testsuite/gcc.dg/Wvla-parameter-12.c | 36 ++++++++++++++++++++++++
gcc/tree-core.h | 7 ++++-
5 files changed, 69 insertions(+), 11 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/Wvla-parameter-12.c
diff --git a/gcc/c-family/c-warn.c b/gcc/c-family/c-warn.c
index 7414063aa11..250da89a829 100644
--- a/gcc/c-family/c-warn.c
+++ b/gcc/c-family/c-warn.c
@@ -3646,7 +3646,8 @@ warn_parm_array_mismatch (location_t origloc, tree fndecl, tree newparms)
/* The VLA bounds don't refer to other function parameters.
Compare them lexicographically to detect gross mismatches
such as between T[foo()] and T[bar()]. */
- if (operand_equal_p (newbnd, curbnd, OEP_LEXICOGRAPHIC))
+ if (operand_equal_p (newbnd, curbnd,
+ OEP_DECL_NAME | OEP_LEXICOGRAPHIC))
continue;
if (warning_at (newloc, OPT_Wvla_parameter,
diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index 53b2b5b637d..ddef9c68fb7 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -5862,6 +5862,7 @@ get_parm_array_spec (const struct c_parm *parm, tree attrs)
/* Each variable VLA bound is represented by a dollar sign. */
spec += "$";
+ STRIP_NOPS (nelts);
vbchain = tree_cons (NULL_TREE, nelts, vbchain);
}
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index a1d08c74025..f5c19a0cfd4 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -3506,11 +3506,26 @@ operand_compare::operand_equal_p (const_tree arg0, const_tree arg1,
case tcc_declaration:
/* Consider __builtin_sqrt equal to sqrt. */
- return (TREE_CODE (arg0) == FUNCTION_DECL
- && fndecl_built_in_p (arg0) && fndecl_built_in_p (arg1)
- && DECL_BUILT_IN_CLASS (arg0) == DECL_BUILT_IN_CLASS (arg1)
- && (DECL_UNCHECKED_FUNCTION_CODE (arg0)
- == DECL_UNCHECKED_FUNCTION_CODE (arg1)));
+ if (TREE_CODE (arg0) == FUNCTION_DECL)
+ return (fndecl_built_in_p (arg0) && fndecl_built_in_p (arg1)
+ && DECL_BUILT_IN_CLASS (arg0) == DECL_BUILT_IN_CLASS (arg1)
+ && (DECL_UNCHECKED_FUNCTION_CODE (arg0)
+ == DECL_UNCHECKED_FUNCTION_CODE (arg1)));
+
+ if (DECL_P (arg0)
+ && (flags & OEP_DECL_NAME)
+ && (flags & OEP_LEXICOGRAPHIC))
+ {
+ /* Consider decls with the same name equal. The caller needs
+ to make sure they refer to the same entity (such as a function
+ formal parameter). */
+ tree a0name = DECL_NAME (arg0);
+ tree a1name = DECL_NAME (arg1);
+ const char *a0ns = a0name ? IDENTIFIER_POINTER (a0name) : NULL;
+ const char *a1ns = a1name ? IDENTIFIER_POINTER (a1name) : NULL;
+ return a0ns && a1ns && strcmp (a0ns, a1ns) == 0;
+ }
+ return false;
case tcc_exceptional:
if (TREE_CODE (arg0) == CONSTRUCTOR)
@@ -3921,14 +3936,14 @@ bool
operand_compare::verify_hash_value (const_tree arg0, const_tree arg1,
unsigned int flags, bool *ret)
{
- /* When checking, verify at the outermost operand_equal_p call that
- if operand_equal_p returns non-zero then ARG0 and ARG1 has the same
- hash value. */
+ /* When checking and unless comparing DECL names, verify that if
+ the outermost operand_equal_p call returns non-zero then ARG0
+ and ARG1 have the same hash value. */
if (flag_checking && !(flags & OEP_NO_HASH_CHECK))
{
if (operand_equal_p (arg0, arg1, flags | OEP_NO_HASH_CHECK))
{
- if (arg0 != arg1)
+ if (arg0 != arg1 && !(flags & OEP_DECL_NAME))
{
inchash::hash hstate0 (0), hstate1 (0);
hash_operand (arg0, hstate0, flags | OEP_HASH_CHECK);
diff --git a/gcc/testsuite/gcc.dg/Wvla-parameter-12.c b/gcc/testsuite/gcc.dg/Wvla-parameter-12.c
new file mode 100644
index 00000000000..1be5e48203b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wvla-parameter-12.c
@@ -0,0 +1,36 @@
+/* PR c/101289 - bogus -Wvla-parameter warning when using const bound
+ { dg-do compile }
+ { dg-options "-Wall" } */
+
+void f1ci_can (const int n, char a[n]);
+void f1ci_can (const int n, char a[n]); // { dg-bogus "-Wvla-parameter" }
+
+void f2ci_can (const int m, char a[m]);
+void f2ci_can (int n, char a[n]); // { dg-bogus "-Wvla-parameter" }
+
+void f3i_can (int n, char a[n]);
+void f3i_can (const int n, char a[n]); // { dg-bogus "-Wvla-parameter" }
+
+void f4i_can (int n, char a[n]);
+void f4i_can (const int n, char a[(int)n]); // { dg-bogus "-Wvla-parameter" }
+
+void f5i_can (int n, char a[(char)n]);
+void f5i_can (const int n, char a[(char)n]); // { dg-bogus "-Wvla-parameter" }
+
+void f6i_can (int m, char a[(char)m]);
+void f6i_can (const int n, char a[(char)n]); // { dg-bogus "-Wvla-parameter" "" { xfail *-*-* } }
+
+
+/* PR c/97548 - bogus -Wvla-parameter on a bound expression involving
+ a parameter */
+
+int n;
+
+void f7ianp1 (int, int[n + 1]);
+void f7ianp1 (int, int[n + 1]);
+void f7ianp1 (int, int[n + 2]); // { dg-warning "-Wvla-parameter" }
+
+void f8iakp1 (int k, int [k + 1]);
+void f8iakp1 (int k, int [k + 1]); // { dg-bogus "-Wvla-parameter" }
+void f8iakp1 (int k, int [1 + k]); // { dg-bogus "-Wvla-parameter" }
+void f8iakp1 (int k, int [k + 2]); // { dg-warning "-Wvla-parameter" }
diff --git a/gcc/tree-core.h b/gcc/tree-core.h
index 07ddf91a230..c31b8ebf249 100644
--- a/gcc/tree-core.h
+++ b/gcc/tree-core.h
@@ -885,6 +885,7 @@ enum size_type_kind {
stk_type_kind_last
};
+/* Flags controlling operand_equal_p() behavior. */
enum operand_equal_flag {
OEP_ONLY_CONST = 1,
OEP_PURE_SAME = 2,
@@ -899,7 +900,11 @@ enum operand_equal_flag {
OEP_BITWISE = 128,
/* For OEP_ADDRESS_OF of COMPONENT_REFs, only consider same fields as
equivalent rather than also different fields with the same offset. */
- OEP_ADDRESS_OF_SAME_FIELD = 256
+ OEP_ADDRESS_OF_SAME_FIELD = 256,
+ /* In conjunction with OEP_LEXICOGRAPHIC considers names of declarations
+ of the same kind. Used to compare VLA bounds involving parameters
+ across redeclarations of the same function. */
+ OEP_DECL_NAME = 512
};
/* Enum and arrays used for tree allocation stats.
--
2.31.1
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