__vfscanf_internal: fix aliasing violation (bug 26690)

Message ID mvmeemi81yq.fsf@suse.de
State New
Headers show
Series
  • __vfscanf_internal: fix aliasing violation (bug 26690)
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Commit Message

Andreas Schwab Oct. 1, 2020, 2:17 p.m.
As noted in <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97264>, the cast
in the call to the read_int function is an aliasing violation.  Change the
type of local variable f to a pointer to unsigned, which allows to
eliminate most casts while only adding three new ones.
---
 stdio-common/vfscanf-internal.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

-- 
2.28.0


-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."

Comments

Adhemerval Zanella via Libc-alpha Oct. 8, 2020, 7:26 a.m. | #1
The 10/01/2020 16:17, Andreas Schwab wrote:
> As noted in <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97264>, the cast

> in the call to the read_int function is an aliasing violation.  Change the

> type of local variable f to a pointer to unsigned, which allows to

> eliminate most casts while only adding three new ones.


this looks good to me.


> ---

>  stdio-common/vfscanf-internal.c | 22 +++++++++++-----------

>  1 file changed, 11 insertions(+), 11 deletions(-)

> 

> diff --git a/stdio-common/vfscanf-internal.c b/stdio-common/vfscanf-internal.c

> index 95b46dcbeb..3a323547f9 100644

> --- a/stdio-common/vfscanf-internal.c

> +++ b/stdio-common/vfscanf-internal.c

> @@ -277,7 +277,7 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,

>  #endif

>  {

>    va_list arg;

> -  const CHAR_T *f = format;

> +  const UCHAR_T *f = (const UCHAR_T *) format;

>    UCHAR_T fc;	/* Current character of the format.  */

>    WINT_T done = 0;	/* Assignments done.  */

>    size_t read_in = 0;	/* Chars read in.  */

> @@ -415,10 +415,11 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,

>  #endif

>  

>  #ifndef COMPILE_WSCANF

> -      if (!isascii ((unsigned char) *f))

> +      if (!isascii (*f))

>  	{

>  	  /* Non-ASCII, may be a multibyte.  */

> -	  int len = __mbrlen (f, strlen (f), &state);

> +	  int len = __mbrlen ((const char *) f, strlen ((const char *) f),

> +			      &state);

>  	  if (len > 0)

>  	    {

>  	      do

> @@ -426,7 +427,7 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,

>  		  c = inchar ();

>  		  if (__glibc_unlikely (c == EOF))

>  		    input_error ();

> -		  else if (c != (unsigned char) *f++)

> +		  else if (c != *f++)

>  		    {

>  		      ungetc_not_eof (c, s);

>  		      conv_error ();

> @@ -484,9 +485,9 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,

>        char_buffer_rewind (&charbuf);

>  

>        /* Check for a positional parameter specification.  */

> -      if (ISDIGIT ((UCHAR_T) *f))

> +      if (ISDIGIT (*f))

>  	{

> -	  argpos = read_int ((const UCHAR_T **) &f);

> +	  argpos = read_int (&f);

>  	  if (*f == L_('$'))

>  	    ++f;

>  	  else

> @@ -521,8 +522,8 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,

>  

>        /* Find the maximum field width.  */

>        width = 0;

> -      if (ISDIGIT ((UCHAR_T) *f))

> -	width = read_int ((const UCHAR_T **) &f);

> +      if (ISDIGIT (*f))

> +	width = read_int (&f);

>      got_width:

>        if (width == 0)

>  	width = -1;

> @@ -2522,12 +2523,11 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,

>  	    }

>  

>  	  while ((fc = *f++) != '\0' && fc != ']')

> -	    if (fc == '-' && *f != '\0' && *f != ']'

> -		&& (unsigned char) f[-2] <= (unsigned char) *f)

> +	    if (fc == '-' && *f != '\0' && *f != ']' && f[-2] <= *f)

>  	      {

>  		/* Add all characters from the one before the '-'

>  		   up to (but not including) the next format char.  */

> -		for (fc = (unsigned char) f[-2]; fc < (unsigned char) *f; ++fc)

> +		for (fc = f[-2]; fc < *f; ++fc)

>  		  ((char *)charbuf.scratch.data)[fc] = 1;

>  	      }

>  	    else

> -- 

> 2.28.0

> 

> 

> -- 

> Andreas Schwab, SUSE Labs, schwab@suse.de

> GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7

> "And now for something completely different."


--

Patch

diff --git a/stdio-common/vfscanf-internal.c b/stdio-common/vfscanf-internal.c
index 95b46dcbeb..3a323547f9 100644
--- a/stdio-common/vfscanf-internal.c
+++ b/stdio-common/vfscanf-internal.c
@@ -277,7 +277,7 @@  __vfscanf_internal (FILE *s, const char *format, va_list argptr,
 #endif
 {
   va_list arg;
-  const CHAR_T *f = format;
+  const UCHAR_T *f = (const UCHAR_T *) format;
   UCHAR_T fc;	/* Current character of the format.  */
   WINT_T done = 0;	/* Assignments done.  */
   size_t read_in = 0;	/* Chars read in.  */
@@ -415,10 +415,11 @@  __vfscanf_internal (FILE *s, const char *format, va_list argptr,
 #endif
 
 #ifndef COMPILE_WSCANF
-      if (!isascii ((unsigned char) *f))
+      if (!isascii (*f))
 	{
 	  /* Non-ASCII, may be a multibyte.  */
-	  int len = __mbrlen (f, strlen (f), &state);
+	  int len = __mbrlen ((const char *) f, strlen ((const char *) f),
+			      &state);
 	  if (len > 0)
 	    {
 	      do
@@ -426,7 +427,7 @@  __vfscanf_internal (FILE *s, const char *format, va_list argptr,
 		  c = inchar ();
 		  if (__glibc_unlikely (c == EOF))
 		    input_error ();
-		  else if (c != (unsigned char) *f++)
+		  else if (c != *f++)
 		    {
 		      ungetc_not_eof (c, s);
 		      conv_error ();
@@ -484,9 +485,9 @@  __vfscanf_internal (FILE *s, const char *format, va_list argptr,
       char_buffer_rewind (&charbuf);
 
       /* Check for a positional parameter specification.  */
-      if (ISDIGIT ((UCHAR_T) *f))
+      if (ISDIGIT (*f))
 	{
-	  argpos = read_int ((const UCHAR_T **) &f);
+	  argpos = read_int (&f);
 	  if (*f == L_('$'))
 	    ++f;
 	  else
@@ -521,8 +522,8 @@  __vfscanf_internal (FILE *s, const char *format, va_list argptr,
 
       /* Find the maximum field width.  */
       width = 0;
-      if (ISDIGIT ((UCHAR_T) *f))
-	width = read_int ((const UCHAR_T **) &f);
+      if (ISDIGIT (*f))
+	width = read_int (&f);
     got_width:
       if (width == 0)
 	width = -1;
@@ -2522,12 +2523,11 @@  __vfscanf_internal (FILE *s, const char *format, va_list argptr,
 	    }
 
 	  while ((fc = *f++) != '\0' && fc != ']')
-	    if (fc == '-' && *f != '\0' && *f != ']'
-		&& (unsigned char) f[-2] <= (unsigned char) *f)
+	    if (fc == '-' && *f != '\0' && *f != ']' && f[-2] <= *f)
 	      {
 		/* Add all characters from the one before the '-'
 		   up to (but not including) the next format char.  */
-		for (fc = (unsigned char) f[-2]; fc < (unsigned char) *f; ++fc)
+		for (fc = f[-2]; fc < *f; ++fc)
 		  ((char *)charbuf.scratch.data)[fc] = 1;
 	      }
 	    else