PR c/85931 - -Wsizeof-pointer-memaccess for strncpy with size of source

gcc/c-family/ChangeLog:

	PR c/85931
	* c-warn.c (sizeof_pointer_memaccess_warning): Avoid warning when
	sizeof source and destination yields the same value.

gcc/ChangeLog:

	PR c/85931
	* fold-const.c (operand_equal_p): Handle SAVE_EXPR.

gcc/testsuite/ChangeLog:

	PR c/85931
	* gcc.dg/Wstringop-truncation-3.c: New test.

From-SVN: r261515

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 48d6d8307b1a3e5ca962fbdf6e17aeb44d5d604d..b1b32998fde38c0853524259538cadde0a5d70c5 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2018-06-12  Martin Sebor  <msebor@redhat.com>
+
+       PR c/85931
+       * fold-const.c (operand_equal_p): Handle SAVE_EXPR.
+
 2018-06-12  Will Schmidt  <will_schmidt@vnet.ibm.com>
 
        * config/rs6000/rs6000-c.c (altivec_overloaded_builtins): Add

diff --git a/gcc/c-family/ChangeLog b/gcc/c-family/ChangeLog
index 9ef0a12eb6afc542f122ec119df13739701ab53d..f63af26624cedd59e87e6f0466515dbb7e779d2d 100644 (file)
--- a/gcc/c-family/ChangeLog
+++ b/gcc/c-family/ChangeLog
@@ -1,3 +1,9 @@
+2018-06-12  Martin Sebor  <msebor@redhat.com>
+
+       PR c/85931
+       * c-warn.c (sizeof_pointer_memaccess_warning): Avoid warning when
+       sizeof source and destination yields the same value.
+
 2018-06-12  Martin Liska  <mliska@suse.cz>
 
        * c.opt: Make MPX-related options as Deprecated.

diff --git a/gcc/c-family/c-warn.c b/gcc/c-family/c-warn.c
index 859d72b3f83fe8742874a0458368877a4d95a2af..95ac09d76a1e7ed67a94c9dd97152e07417e046f 100644 (file)
--- a/gcc/c-family/c-warn.c
+++ b/gcc/c-family/c-warn.c
@@ -792,13 +792,26 @@ sizeof_pointer_memaccess_warning (location_t *sizeof_arg_loc, tree callee,
     {
       /* The argument type may be an array.  Diagnose bounded string
         copy functions that specify the bound in terms of the source
-        argument rather than the destination.  */
+        argument rather than the destination unless they are equal
+        to one another.  Handle constant sizes and also try to handle
+        sizeof expressions involving VLAs.  */
       if (strop && !cmp && fncode != BUILT_IN_STRNDUP && src)
        {
          tem = tree_strip_nop_conversions (src);
          if (TREE_CODE (tem) == ADDR_EXPR)
            tem = TREE_OPERAND (tem, 0);
-         if (operand_equal_p (tem, sizeof_arg[idx], OEP_ADDRESS_OF))
+
+         tree d = tree_strip_nop_conversions (dest);
+         if (TREE_CODE (d) == ADDR_EXPR)
+           d = TREE_OPERAND (d, 0);
+
+         tree dstsz = TYPE_SIZE_UNIT (TREE_TYPE (d));
+         tree srcsz = TYPE_SIZE_UNIT (TREE_TYPE (tem));
+
+         if ((!dstsz
+              || !srcsz
+              || !operand_equal_p (dstsz, srcsz, OEP_LEXICOGRAPHIC))
+             && operand_equal_p (tem, sizeof_arg[idx], OEP_ADDRESS_OF))
            warning_at (sizeof_arg_loc[idx], OPT_Wsizeof_pointer_memaccess,
                        "argument to %<sizeof%> in %qD call is the same "
                        "expression as the source; did you mean to use "

diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 1e8d79e40221ae93cc06b5896dc9312926917acf..c85a99124351889dd7272b331e46af3188ac668e 100644 (file)
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -3358,6 +3358,7 @@ operand_equal_p (const_tree arg0, const_tree arg1, unsigned int flags)
 
        case CLEANUP_POINT_EXPR:
        case EXPR_STMT:
+       case SAVE_EXPR:
          if (flags & OEP_LEXICOGRAPHIC)
            return OP_SAME (0);
          return 0;

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 088f5c2ff7fda1bfd2e63e0b383535029f58ab7e..f9c8d93d3d352d0ad9713f4bbce90e6b47291bfb 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2018-06-12  Martin Sebor  <msebor@redhat.com>
+
+       PR c/85931
+       * gcc.dg/Wstringop-truncation-3.c: New test.
+
 2018-06-12  Will Schmidt  <will_schmidt@vnet.ibm.com>
 
        * gcc.target/powerpc/p8-vec-xl-xst-v2.c: New.

diff --git a/gcc/testsuite/gcc.dg/Wstringop-truncation-3.c b/gcc/testsuite/gcc.dg/Wstringop-truncation-3.c
new file mode 100644 (file)
index 0000000..57f4d64
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wstringop-truncation-3.c
@@ -0,0 +1,59 @@
+/* PR c/85931 - -Wsizeof-pointer-memaccess for strncpy with size of source
+   { dg-do compile }
+   { dg-options "-O2 -Wall -Wstringop-truncation -ftrack-macro-expansion=0" } */
+
+typedef __SIZE_TYPE__ size_t;
+
+extern char* strncpy (char*, const char*, size_t);
+
+extern char a3[3], b3[3];
+extern char a5[5], b5[5];
+extern char ax[], bx[];
+
+struct SA
+{
+  char a3[3], b3[3];
+  char a5[5], b5[5];
+  char ax[];
+};
+
+void sink (void*, ...);
+
+#define T(d, s, n)   sink (strncpy (d, s, n))
+
+void test_array (unsigned n)
+{
+  T (a3, b3, 3);
+  /* For the following statemenmt, GCC 8.1 issues warning:
+
+       argument to ‘sizeof’ in ‘strncpy’ call is the same expression
+       as the source; did you mean to use the size of the destination?
+
+     Since the size of both the source and destination the warning
+     isn't helpful.  Verify that it isn't issued.  */
+  T (a3, b3, sizeof b3);    /* { dg-bogus "\\\[-Wsizeof-pointer-memaccess" } */
+
+  T (a3, ax, sizeof a3);    /* { dg-warning "\\\[-Wstringop-truncation" } */
+  T (ax, a3, sizeof a3);    /* { dg-warning "argument to .sizeof. in .strncpy. call is the same expression as the source" } */
+
+  char an[n], bn[n];
+  sink (an, bn);
+
+  T (an, bn, sizeof bn);    /* { dg-bogus "\\\[-Wsizeof-pointer-memaccess" } */
+}
+
+void test_member_array (struct SA *sa, unsigned n)
+{
+  T (sa->a3, sa->b3, 3);
+  T (sa->a3, sa->b3, sizeof sa->b3);  /* { dg-bogus "\\\[-Wsizeof-pointer-memaccess" } */
+
+  T (sa->a3, sa->ax, sizeof sa->a3);  /* { dg-warning "\\\[-Wstringop-truncation" } */
+  T (sa->ax, sa->a3, sizeof sa->a3);  /* { dg-warning "argument to .sizeof. in .strncpy. call is the same expression as the source" } */
+
+  struct VarLenStruct {
+    char an[n], bn[n];
+  } x;
+
+  sink (&x);
+  T (x.an, x.bn, sizeof x.bn);        /* { dg-bogus "\\\[-Wsizeof-pointer-memaccess" } */
+}