public inbox for gcc-patches@gcc.gnu.org
 help / color / mirror / Atom feed
* -Wformat-overflow handling for %b and %B directives in C2X standard
@ 2022-04-01 19:19 Frolov Daniil
  2022-04-01 20:15 ` Marek Polacek
  0 siblings, 1 reply; 8+ messages in thread
From: Frolov Daniil @ 2022-04-01 19:19 UTC (permalink / raw)
  To: gcc-patches

[-- Attachment #1: Type: text/plain, Size: 216 bytes --]

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.

[-- Attachment #2: 0001-Support-b-B-for-Wformat-overflow-sprintf-snprintf.patch --]
[-- Type: text/x-patch, Size: 6476 bytes --]

From 2051344e9500651f6e94c44cbc7820715382b957 Mon Sep 17 00:00:00 2001
From: Frolov Daniil <frolov.da@phystech.edu>
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


^ permalink raw reply	[flat|nested] 8+ messages in thread
end of thread, other threads:[~2022-11-28 17:36 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-04-01 19:19 -Wformat-overflow handling for %b and %B directives in C2X standard Frolov Daniil
2022-04-01 20:15 ` Marek Polacek
2022-04-06 21:10   ` Frolov Daniil
2022-04-11 21:56     ` Marek Polacek
2022-08-15 16:42       ` Frolov Daniil
2022-08-30 14:56         ` Marek Polacek
2022-09-01  9:41           ` Даниил Александрович Фролов
2022-11-28 17:36             ` Jeff Law

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).