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PR middle-end/93646 - confusing -Wstringop-truncation on strncat where -Wstringop-overflow is expected

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gcc/ChangeLog:

	PR middle-end/93646
	* tree-ssa-strlen.c (handle_builtin_stxncpy): Rename...
	(handle_builtin_stxncpy_strncat): ...to this.  Change first argument.
	Issue only -Wstringop-overflow strncat, never -Wstringop-truncation.
	(strlen_check_and_optimize_call): Adjust callee name.

gcc/testsuite/ChangeLog:

	PR middle-end/93646
	* gcc.dg/Wstringop-overflow-31.c: New test.
This commit is contained in:
Martin Sebor 2020-02-12 13:53:49 -07:00
parent 37462a131c
commit 0a0de9636d
4 changed files with 67 additions and 12 deletions
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8
gcc/ChangeLog
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@ -1,3 +1,11 @@
2020-02-12 Martin Sebor <msebor@redhat.com>
PR middle-end/93646
* tree-ssa-strlen.c (handle_builtin_stxncpy): Rename...
(handle_builtin_stxncpy_strncat): ...to this. Change first argument.
Issue only -Wstringop-overflow strncat, never -Wstringop-truncation.
(strlen_check_and_optimize_call): Adjust callee name.
2020-02-12 Jeff Law <law@redhat.com>
* config/h8300/h8300.md (comparison shortening peepholes): Drop

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2020-02-12 Martin Sebor <msebor@redhat.com>
PR middle-end/93646
* gcc.dg/Wstringop-overflow-31.c: New test.
2020-02-12 Wilco Dijkstra <wdijkstr@arm.com>
PR rtl-optimization/93565

40
gcc/testsuite/gcc.dg/Wstringop-overflow-31.c Normal file
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@ -0,0 +1,40 @@
/* PR middle-end/93646 - confusing -Wstringop-truncation on strncat where
-Wstringop-overflow is expected
{ dg-do compile }
{ dg-options "-O2 -Wall" } */
extern __SIZE_TYPE__ strlen (const char*);
extern char* strncat (char*, const char*, __SIZE_TYPE__);
char a[4];
void f0 (char *d, const char *s)
{
strncat (d, s, strlen (s)); // { dg-warning "specified bound depends on the length of the source argument" }
/* { dg-message "function 'f0'.*inlined from 'f1'" "inlining stack" { target *-*-* } 0 } */
// Prevent f0 from being replaced by g0.
*d = 'f';
}
void f1 (const char *s)
{
f0 (a, s);
}
static void g0 (char *d, const char *s)
{
strncat (d, s, strlen (s)); // { dg-warning "specified bound 3 equals source length" }
/* { dg-message "function 'g0'.*inlined from 'g1'" "inlining stack" { target *-*-* } 0 } */
// Prevent g0 from being replaced by f0.
*d = 'g';
}
void g1 (void)
{
g0 (a, "123");
}

26
gcc/tree-ssa-strlen.c
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@ -192,7 +192,7 @@ struct laststmt_struct
} laststmt;
static int get_stridx_plus_constant (strinfo *, unsigned HOST_WIDE_INT, tree);
static void handle_builtin_stxncpy (built_in_function, gimple_stmt_iterator *);
static void handle_builtin_stxncpy_strncat (bool, gimple_stmt_iterator *);
/* Sets MINMAX to either the constant value or the range VAL is in
and returns either the constant value or VAL on success or null
@ -2876,10 +2876,10 @@ handle_builtin_strcpy (enum built_in_function bcode, gimple_stmt_iterator *gsi,
and if so, issue an appropriate warning. */
static void
handle_builtin_strncat (built_in_function bcode, gimple_stmt_iterator *gsi)
handle_builtin_strncat (built_in_function, gimple_stmt_iterator *gsi)
{
/* Same as stxncpy(). */
handle_builtin_stxncpy (bcode, gsi);
handle_builtin_stxncpy_strncat (true, gsi);
}
/* Return true if LEN depends on a call to strlen(SRC) in an interesting
@ -2974,8 +2974,8 @@ is_strlen_related_p (tree src, tree len)
return false;
}
/* Called by handle_builtin_stxncpy and by gimple_fold_builtin_strncpy
in gimple-fold.c.
/* Called by handle_builtin_stxncpy_strncat and by
gimple_fold_builtin_strncpy in gimple-fold.c.
Check to see if the specified bound is a) equal to the size of
the destination DST and if so, b) if it's immediately followed by
DST[CNT - 1] = '\0'. If a) holds and b) does not, warn. Otherwise,
@ -3283,13 +3283,14 @@ maybe_diag_stxncpy_trunc (gimple_stmt_iterator gsi, tree src, tree cnt)
return false;
}
/* Check the arguments to the built-in forms of stpncpy and strncpy for
out-of-bounds offsets or overlapping access, and to see if the size
is derived from calling strlen() on the source argument, and if so,
issue the appropriate warning. */
/* Check the arguments to the built-in forms of stpncpy, strncpy, and
strncat, for out-of-bounds offsets or overlapping access, and to see
if the size is derived from calling strlen() on the source argument,
and if so, issue the appropriate warning.
APPEND_P is true for strncat. */
static void
handle_builtin_stxncpy (built_in_function, gimple_stmt_iterator *gsi)
handle_builtin_stxncpy_strncat (bool append_p, gimple_stmt_iterator *gsi)
{
if (!strlen_to_stridx)
return;
@ -3385,7 +3386,8 @@ handle_builtin_stxncpy (built_in_function, gimple_stmt_iterator *gsi)
whether its value is known. Otherwise, issue the more generic
-Wstringop-overflow which triggers for LEN arguments that in
any meaningful way depend on strlen(SRC). */
if (sisrc == silen
if (!append_p
&& sisrc == silen
&& is_strlen_related_p (src, len)
&& warning_at (callloc, OPT_Wstringop_truncation,
"%G%qD output truncated before terminating nul "
@ -5352,7 +5354,7 @@ strlen_check_and_optimize_call (gimple_stmt_iterator *gsi, bool *zero_write,
case BUILT_IN_STPNCPY_CHK:
case BUILT_IN_STRNCPY:
case BUILT_IN_STRNCPY_CHK:
handle_builtin_stxncpy (DECL_FUNCTION_CODE (callee), gsi);
handle_builtin_stxncpy_strncat (false, gsi);
break;
case BUILT_IN_MEMCPY: