Hello, I've noticed that -Wformat-overflow doesn't handle %b and %B
directives in the sprintf function. I've added a relevant issue in bugzilla
(bug #105129).
I attach a patch with a possible solution to the letter.
From 2051344e9500651f6e94c44cbc7820715382b957 Mon Sep 17 00:00:00 2001
From: Frolov Daniil <[email protected]>
Date: Fri, 1 Apr 2022 00:47:03 +0500
Subject: [PATCH] Support %b, %B for -Wformat-overflow (sprintf, snprintf)
testsuite: add tests to check -Wformat-overflow on %b.
Wformat-overflow1.c is compiled using -std=c2x so warning has to
be throwed
Wformat-overflow2.c doesn't throw warnings cause c2x std isn't
used
gcc/ChangeLog:
* gimple-ssa-sprintf.cc
(check_std_c2x): New function
(fmtresult::type_max_digits): add base == 2 handling
(tree_digits): add handle for base == 2
(format_integer): now handle %b and %B using base = 2
(parse_directive): add cases to handle %b and %B directives
(compute_format_length): add handling for base = 2
gcc/testsuite/ChangeLog:
* gcc.dg/Wformat-overflow1.c: New test. (using -std=c2x)
* gcc.dg/Wformat-overflow2.c: New test. (-std=c11 no warning)
---
gcc/gimple-ssa-sprintf.cc | 42 ++++++++++++++++++++----
gcc/testsuite/gcc.dg/Wformat-overflow1.c | 28 ++++++++++++++++
gcc/testsuite/gcc.dg/Wformat-overflow2.c | 16 +++++++++
3 files changed, 79 insertions(+), 7 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/Wformat-overflow1.c
create mode 100644 gcc/testsuite/gcc.dg/Wformat-overflow2.c
diff --git a/gcc/gimple-ssa-sprintf.cc b/gcc/gimple-ssa-sprintf.cc
index c93f12f90b5..7f68c2b6e51 100644
--- a/gcc/gimple-ssa-sprintf.cc
+++ b/gcc/gimple-ssa-sprintf.cc
@@ -107,6 +107,15 @@ namespace {
static int warn_level;
+/* b_overflow_flag depends on the current standart when using gcc */
+static bool b_overflow_flag;
+
+/* check is current standart version equals C2X*/
+static bool check_std_c2x ()
+{
+ return !strcmp (lang_hooks.name, "GNU C2X");
+}
+
/* The minimum, maximum, likely, and unlikely maximum number of bytes
of output either a formatting function or an individual directive
can result in. */
@@ -535,6 +544,8 @@ fmtresult::type_max_digits (tree type, int base)
unsigned prec = TYPE_PRECISION (type);
switch (base)
{
+ case 2:
+ return prec;
case 8:
return (prec + 2) / 3;
case 10:
@@ -857,11 +868,11 @@ tree_digits (tree x, int base, HOST_WIDE_INT prec, bool plus, bool prefix)
/* Adjust a non-zero value for the base prefix, either hexadecimal,
or, unless precision has resulted in a leading zero, also octal. */
- if (prefix && absval && (base == 16 || prec <= ndigs))
+ if (prefix && absval && (base == 2 || base == 16 || prec <= ndigs))
{
if (base == 8)
res += 1;
- else if (base == 16)
+ else if (base == 16 || base == 2) /*0x...(0X...) and 0b...(0B...)*/
res += 2;
}
@@ -1229,6 +1240,10 @@ format_integer (const directive &dir, tree arg, pointer_query &ptr_qry)
case 'u':
base = 10;
break;
+ case 'b':
+ case 'B':
+ base = 2;
+ break;
case 'o':
base = 8;
break;
@@ -1351,10 +1366,10 @@ format_integer (const directive &dir, tree arg, pointer_query &ptr_qry)
/* Bump up the counters if WIDTH is greater than LEN. */
res.adjust_for_width_or_precision (dir.width, dirtype, base,
- (sign | maybebase) + (base == 16));
+ (sign | maybebase) + (base == 2 || base == 16));
/* Bump up the counters again if PRECision is greater still. */
res.adjust_for_width_or_precision (dir.prec, dirtype, base,
- (sign | maybebase) + (base == 16));
+ (sign | maybebase) + (base == 2 || base == 16));
return res;
}
@@ -1503,7 +1518,7 @@ format_integer (const directive &dir, tree arg, pointer_query &ptr_qry)
if (res.range.min == 1)
res.range.likely += base == 8 ? 1 : 2;
else if (res.range.min == 2
- && base == 16
+ && (base == 16 || base == 2)
&& (dir.width[0] == 2 || dir.prec[0] == 2))
++res.range.likely;
}
@@ -1511,9 +1526,9 @@ format_integer (const directive &dir, tree arg, pointer_query &ptr_qry)
res.range.unlikely = res.range.max;
res.adjust_for_width_or_precision (dir.width, dirtype, base,
- (sign | maybebase) + (base == 16));
+ (sign | maybebase) + (base == 2 || base == 16));
res.adjust_for_width_or_precision (dir.prec, dirtype, base,
- (sign | maybebase) + (base == 16));
+ (sign | maybebase) + (base == 2 || base == 16));
return res;
}
@@ -3680,6 +3695,8 @@ parse_directive (call_info &info,
++pf;
break;
}
+
+
switch (target_to_host (*pf))
{
@@ -3713,6 +3730,14 @@ parse_directive (call_info &info,
case 'X':
dir.fmtfunc = format_integer;
break;
+
+ case 'b':
+ case 'B':
+ if (b_overflow_flag) {
+ dir.fmtfunc = format_integer;
+ break;
+ }
+ return 0;
case 'p':
/* The %p output is implementation-defined. It's possible
@@ -4038,6 +4063,9 @@ compute_format_length (call_info &info, format_result *res,
bool success = true;
+ /* Check for GNU C2X standart */
+ b_overflow_flag = check_std_c2x ();
+
for (const char *pf = info.fmtstr; ; ++dirno)
{
directive dir (&info, dirno);
diff --git a/gcc/testsuite/gcc.dg/Wformat-overflow1.c b/gcc/testsuite/gcc.dg/Wformat-overflow1.c
new file mode 100644
index 00000000000..cf9766fae14
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wformat-overflow1.c
@@ -0,0 +1,28 @@
+/*
+ { dg-do compile }
+ { dg-options "-Wformat-overflow -std=c2x" }
+*/
+
+extern int sprintf (char* restrict, const char* restrict, ...);
+
+void test_warn () {
+
+ int n = __INT_MAX__;
+ char dst [5] = {0};
+ sprintf (dst, "%b", n); /* { dg-warning "-Wformat-overflow" } */
+
+ sprintf (dst, "%#b", n); /* { dg-warning "-Wformat-overflow" } */
+
+}
+
+void test_no_warn () {
+
+ char dst [5] = {0};
+ int n = 8;
+ sprintf (dst, "%b", n);
+
+ char another_dst [34] = {0};
+ n = __INT_MAX__;
+ sprintf (another_dst, "%#b", n);
+
+}
diff --git a/gcc/testsuite/gcc.dg/Wformat-overflow2.c b/gcc/testsuite/gcc.dg/Wformat-overflow2.c
new file mode 100644
index 00000000000..c6b1d9062a6
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wformat-overflow2.c
@@ -0,0 +1,16 @@
+/*
+ { dg-do compile }
+ { dg-options "-Wformat-overflow -std=c11" }
+*/
+
+extern int sprintf (char* restrict, const char* restrict, ...);
+
+void test_no_warn () {
+
+ /*There is no reason to throw warning if std < c2x*/
+
+ char dst [5] = {0};
+ int n = 32;
+ sprintf (dst, "%b", n);
+
+}
--
2.25.1
