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PR tree-optimization/85700 - Spurious -Wstringop-truncation warning with strncat 

gcc/ChangeLog:

	PR tree-optimization/85700
	* gimple-fold.c (gimple_fold_builtin_strncat): Adjust comment.
	* tree-ssa-strlen.c (is_strlen_related_p): Handle integer subtraction.
	(maybe_diag_stxncpy_trunc): Distinguish strncat from strncpy.

gcc/testsuite/ChangeLog:

	PR tree-optimization/85700
	* gcc.dg/Wstringop-truncation-4.c: New test.

From-SVN: r262110
This commit is contained in:
Martin Sebor 2018-06-25 20:33:28 +00:00 committed by Martin Sebor
parent 2bcd87a7b5
commit eec5f615cb
5 changed files with 125 additions and 38 deletions
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7
gcc/ChangeLog
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@ -1,3 +1,10 @@
2018-06-25 Martin Sebor <msebor@redhat.com>
PR tree-optimization/85700
* gimple-fold.c (gimple_fold_builtin_strncat): Adjust comment.
* tree-ssa-strlen.c (is_strlen_related_p): Handle integer subtraction.
(maybe_diag_stxncpy_trunc): Distinguish strncat from strncpy.
2018-06-25 Martin Sebor <msebor@redhat.com>
* doc/extend.texi (Zero-length arrays): Update and clarify.

8
gcc/gimple-fold.c
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@ -2051,10 +2051,12 @@ gimple_fold_builtin_strncat (gimple_stmt_iterator *gsi)
if (!nowarn && cmpsrc == 0)
{
tree fndecl = gimple_call_fndecl (stmt);
/* To avoid certain truncation the specified bound should also
not be equal to (or less than) the length of the source. */
location_t loc = gimple_location (stmt);
/* To avoid possible overflow the specified bound should also
not be equal to the length of the source, even when the size
of the destination is unknown (it's not an uncommon mistake
to specify as the bound to strncpy the length of the source). */
if (warning_at (loc, OPT_Wstringop_overflow_,
"%G%qD specified bound %E equals source length",
stmt, fndecl, len))

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2018-06-25 Martin Sebor <msebor@redhat.com>
PR tree-optimization/85700
* gcc.dg/Wstringop-truncation-4.c: New test.
2018-06-25 Fritz Reese <fritzoreese@gmail.com>
PR fortran/82972

63
gcc/testsuite/gcc.dg/Wstringop-truncation-4.c Normal file
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@ -0,0 +1,63 @@
/* PR tree-optimization/85700 - Spurious -Wstringop-truncation warning
with strncat
{ dg-do compile }
{ dg-options "-O2 -Wno-stringop-overflow -Wstringop-truncation -ftrack-macro-expansion=0" } */
#define NOIPA __attribute__ ((noipa))
#define strncat __builtin_strncat
#define strlen __builtin_strlen
extern char a4[4], b4[4], ax[];
NOIPA void cat_a4_s1_1 (void)
{
/* There is no truncation here but since the bound of 1 equals
the length of the source string it's likely a mistake that
could cause overflow so it's diagnosed by -Wstringop-overflow */
strncat (a4, "1", 1);
}
NOIPA void cat_a4_s1_2 (void)
{
strncat (a4, "1", 2);
}
NOIPA void cat_a4_s1_3 (void)
{
strncat (a4, "1", 3);
}
NOIPA void cat_a4_s1_4 (void)
{
/* There is no truncation here but since the bound of 1 equals
the length of the source string it's likely a mistake that
could cause overflow so it's diagnosed by -Wstringop-overflow */
strncat (a4, "1", 4);
}
NOIPA void cat_a4_s1_5 (void)
{
/* A bound in excess of the destination size is diagnosed by
-Wstringop-overflow. */
strncat (a4, "1", 5);
}
NOIPA void cat_a4_s1_dlen (void)
{
strncat (a4, "1", sizeof a4 - strlen (a4) - 1);
}
NOIPA void cat_a4_s2_dlen (void)
{
strncat (a4, "12", sizeof a4 - strlen (a4) - 1); /* { dg-bogus "\\\[-Wstringop-truncation]" } */
}
NOIPA void cat_a4_b4_dlen (void)
{
strncat (a4, b4, sizeof a4 - strlen (a4) - 1); /* { dg-bogus "\\\[-Wstringop-truncation]" } */
}
NOIPA void cat_ax_b4_dlen (void)
{
strncat (ax, b4, 32 - strlen (ax) - 1); /* { dg-bogus "\\\[-Wstringop-truncation]" } */
}

80
gcc/tree-ssa-strlen.c
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@ -2014,6 +2014,12 @@ maybe_diag_stxncpy_trunc (gimple_stmt_iterator gsi, tree src, tree cnt)
gcall *call = as_a <gcall *> (stmt);
/* Set to true for strncat whose bound is derived from the length
of the destination (the expected usage pattern). */
bool cat_dstlen_bounded = false;
if (DECL_FUNCTION_CODE (func) == BUILT_IN_STRNCAT)
cat_dstlen_bounded = is_strlen_related_p (dst, cnt);
if (lenrange[0] == cntrange[1] && cntrange[0] == cntrange[1])
return warning_n (callloc, OPT_Wstringop_truncation,
cntrange[0].to_uhwi (),
@ -2024,46 +2030,50 @@ maybe_diag_stxncpy_trunc (gimple_stmt_iterator gsi, tree src, tree cnt)
"copying %E bytes from a string of the same "
"length",
call, func, cnt);
else if (wi::geu_p (lenrange[0], cntrange[1]))
else if (!cat_dstlen_bounded)
{
/* The shortest string is longer than the upper bound of
the count so the truncation is certain. */
if (cntrange[0] == cntrange[1])
return warning_n (callloc, OPT_Wstringop_truncation,
cntrange[0].to_uhwi (),
"%G%qD output truncated copying %E byte "
"from a string of length %wu",
"%G%qD output truncated copying %E bytes "
"from a string of length %wu",
call, func, cnt, lenrange[0].to_uhwi ());
if (wi::geu_p (lenrange[0], cntrange[1]))
{
/* The shortest string is longer than the upper bound of
the count so the truncation is certain. */
if (cntrange[0] == cntrange[1])
return warning_n (callloc, OPT_Wstringop_truncation,
cntrange[0].to_uhwi (),
"%G%qD output truncated copying %E byte "
"from a string of length %wu",
"%G%qD output truncated copying %E bytes "
"from a string of length %wu",
call, func, cnt, lenrange[0].to_uhwi ());
return warning_at (callloc, OPT_Wstringop_truncation,
"%G%qD output truncated copying between %wu "
"and %wu bytes from a string of length %wu",
call, func, cntrange[0].to_uhwi (),
cntrange[1].to_uhwi (), lenrange[0].to_uhwi ());
}
else if (wi::geu_p (lenrange[1], cntrange[1]))
{
/* The longest string is longer than the upper bound of
the count so the truncation is possible. */
if (cntrange[0] == cntrange[1])
return warning_n (callloc, OPT_Wstringop_truncation,
cntrange[0].to_uhwi (),
"%G%qD output may be truncated copying %E "
"byte from a string of length %wu",
"%G%qD output may be truncated copying %E "
"bytes from a string of length %wu",
call, func, cnt, lenrange[1].to_uhwi ());
return warning_at (callloc, OPT_Wstringop_truncation,
"%G%qD output truncated copying between %wu "
"and %wu bytes from a string of length %wu",
call, func, cntrange[0].to_uhwi (),
cntrange[1].to_uhwi (), lenrange[0].to_uhwi ());
}
else if (wi::geu_p (lenrange[1], cntrange[1]))
{
/* The longest string is longer than the upper bound of
the count so the truncation is possible. */
if (cntrange[0] == cntrange[1])
return warning_n (callloc, OPT_Wstringop_truncation,
cntrange[0].to_uhwi (),
"%G%qD output may be truncated copying %E "
"byte from a string of length %wu",
"%G%qD output may be truncated copying %E "
"bytes from a string of length %wu",
call, func, cnt, lenrange[1].to_uhwi ());
return warning_at (callloc, OPT_Wstringop_truncation,
"%G%qD output may be truncated copying between %wu "
"and %wu bytes from a string of length %wu",
call, func, cntrange[0].to_uhwi (),
cntrange[1].to_uhwi (), lenrange[1].to_uhwi ());
return warning_at (callloc, OPT_Wstringop_truncation,
"%G%qD output may be truncated copying between "
"%wu and %wu bytes from a string of length %wu",
call, func, cntrange[0].to_uhwi (),
cntrange[1].to_uhwi (), lenrange[1].to_uhwi ());
}
}
if (cntrange[0] != cntrange[1]
if (!cat_dstlen_bounded
&& cntrange[0] != cntrange[1]
&& wi::leu_p (cntrange[0], lenrange[0])
&& wi::leu_p (cntrange[1], lenrange[0] + 1))
{