[v3,02/10] libio: Improve fortify with clang

  It improve fortify checks for sprintf, vsprintf, vsnsprintf, fprintf,
dprintf, asprintf, __asprintf, obstack_printf, gets, fgets,
fgets_unlocked, fread, and fread_unlocked.  The runtime checks have
similar support coverage as with GCC.

For function with variadic argument (sprintf, snprintf, fprintf, printf,
dprintf, asprintf, __asprintf, obstack_printf) the fortify wrapper calls
the va_arg version since clang does not support __va_arg_pack.

Checked on aarch64, armhf, x86_64, and i686.
---
 libio/bits/stdio2.h | 173 +++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 153 insertions(+), 20 deletions(-)
  

On 2/8/24 13:46, Adhemerval Zanella wrote:
> It improve fortify checks for sprintf, vsprintf, vsnsprintf, fprintf,
> dprintf, asprintf, __asprintf, obstack_printf, gets, fgets,
> fgets_unlocked, fread, and fread_unlocked.  The runtime checks have
> similar support coverage as with GCC.

LGTM.

Tested on x86_64 and i686 with gcc.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>

> For function with variadic argument (sprintf, snprintf, fprintf, printf,
> dprintf, asprintf, __asprintf, obstack_printf) the fortify wrapper calls
> the va_arg version since clang does not support __va_arg_pack.
> 
> Checked on aarch64, armhf, x86_64, and i686.
> ---
>  libio/bits/stdio2.h | 173 +++++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 153 insertions(+), 20 deletions(-)
> 
> diff --git a/libio/bits/stdio2.h b/libio/bits/stdio2.h
> index f9e8d37610..91a80dd7c6 100644
> --- a/libio/bits/stdio2.h
> +++ b/libio/bits/stdio2.h
> @@ -31,15 +31,29 @@ __NTH (sprintf (char *__restrict __s, const char *__restrict __fmt, ...))
>  				  __glibc_objsize (__s), __fmt,
>  				  __va_arg_pack ());
>  }
> +#elif __fortify_use_clang
> +/* clang does not have __va_arg_pack, so defer to va_arg version.  */
> +__fortify_function_error_function __attribute_overloadable__ int
> +__NTH (sprintf (__fortify_clang_overload_arg (char *, __restrict, __s),
> +		const char *__restrict __fmt, ...))
> +{
> +  __gnuc_va_list __fortify_ap;
> +  __builtin_va_start (__fortify_ap, __fmt);
> +  int __r = __builtin___vsprintf_chk (__s, __USE_FORTIFY_LEVEL - 1,
> +				      __glibc_objsize (__s), __fmt,
> +				      __fortify_ap);
> +  __builtin_va_end (__fortify_ap);
> +  return __r;
> +}
>  #elif !defined __cplusplus
>  # define sprintf(str, ...) \
>    __builtin___sprintf_chk (str, __USE_FORTIFY_LEVEL - 1,		      \
>  			   __glibc_objsize (str), __VA_ARGS__)
>  #endif
>  
> -__fortify_function int
> -__NTH (vsprintf (char *__restrict __s, const char *__restrict __fmt,
> -		 __gnuc_va_list __ap))
> +__fortify_function __attribute_overloadable__ int
> +__NTH (vsprintf (__fortify_clang_overload_arg (char *, __restrict, __s),
> +		 const char *__restrict __fmt, __gnuc_va_list __ap))
>  {
>    return __builtin___vsprintf_chk (__s, __USE_FORTIFY_LEVEL - 1,
>  				   __glibc_objsize (__s), __fmt, __ap);
> @@ -55,15 +69,33 @@ __NTH (snprintf (char *__restrict __s, size_t __n,
>  				   __glibc_objsize (__s), __fmt,
>  				   __va_arg_pack ());
>  }
> +# elif __fortify_use_clang
> +/* clang does not have __va_arg_pack, so defer to va_arg version.  */
> +__fortify_function_error_function __attribute_overloadable__ int
> +__NTH (snprintf (__fortify_clang_overload_arg (char *, __restrict, __s),
> +		 size_t __n, const char *__restrict __fmt, ...))
> +{
> +  __gnuc_va_list __fortify_ap;
> +  __builtin_va_start (__fortify_ap, __fmt);
> +  int __r = __builtin___vsnprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
> +				       __glibc_objsize (__s), __fmt,
> +				       __fortify_ap);
> +  __builtin_va_end (__fortify_ap);
> +  return __r;
> +}
>  # elif !defined __cplusplus
>  #  define snprintf(str, len, ...) \
>    __builtin___snprintf_chk (str, len, __USE_FORTIFY_LEVEL - 1,		      \
>  			    __glibc_objsize (str), __VA_ARGS__)
>  # endif
>  
> -__fortify_function int
> -__NTH (vsnprintf (char *__restrict __s, size_t __n,
> -		  const char *__restrict __fmt, __gnuc_va_list __ap))
> +__fortify_function __attribute_overloadable__ int
> +__NTH (vsnprintf (__fortify_clang_overload_arg (char *, __restrict, __s),
> +		  size_t __n, const char *__restrict __fmt,
> +		  __gnuc_va_list __ap))
> +     __fortify_clang_warning (__fortify_clang_bos_static_lt (__n, __s),
> +			      "call to vsnprintf may overflow the destination "
> +			      "buffer")

OK.

>  {
>    return __builtin___vsnprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
>  				    __glibc_objsize (__s), __fmt, __ap);
> @@ -85,6 +117,30 @@ printf (const char *__restrict __fmt, ...)
>  {
>    return __printf_chk (__USE_FORTIFY_LEVEL - 1, __fmt, __va_arg_pack ());
>  }
> +# elif __fortify_use_clang
> +/* clang does not have __va_arg_pack, so defer to va_arg version.  */
> +__fortify_function_error_function __attribute_overloadable__ __nonnull ((1)) int
> +fprintf (__fortify_clang_overload_arg (FILE *, __restrict, __stream),
> +	 const char *__restrict __fmt, ...)
> +{
> +  __gnuc_va_list __fortify_ap;
> +  __builtin_va_start (__fortify_ap, __fmt);
> +  int __r = __builtin___vfprintf_chk (__stream, __USE_FORTIFY_LEVEL - 1,
> +				      __fmt, __fortify_ap);
> +  __builtin_va_end (__fortify_ap);
> +  return __r;
> +}
> +
> +__fortify_function_error_function __attribute_overloadable__ int
> +printf (__fortify_clang_overload_arg (const char *, __restrict, __fmt), ...)
> +{
> +  __gnuc_va_list __fortify_ap;
> +  __builtin_va_start (__fortify_ap, __fmt);
> +  int __r = __builtin___vprintf_chk (__USE_FORTIFY_LEVEL - 1, __fmt,
> +				     __fortify_ap);
> +  __builtin_va_end (__fortify_ap);
> +  return __r;
> +}
>  # elif !defined __cplusplus
>  #  define printf(...) \
>    __printf_chk (__USE_FORTIFY_LEVEL - 1, __VA_ARGS__)
> @@ -92,8 +148,9 @@ printf (const char *__restrict __fmt, ...)
>    __fprintf_chk (stream, __USE_FORTIFY_LEVEL - 1, __VA_ARGS__)
>  # endif
>  
> -__fortify_function int
> -vprintf (const char *__restrict __fmt, __gnuc_va_list __ap)
> +__fortify_function __attribute_overloadable__ int
> +vprintf (__fortify_clang_overload_arg (const char *, __restrict, __fmt),
> +	 __gnuc_va_list __ap)
>  {
>  #ifdef __USE_EXTERN_INLINES
>    return __vfprintf_chk (stdout, __USE_FORTIFY_LEVEL - 1, __fmt, __ap);
> @@ -117,6 +174,18 @@ dprintf (int __fd, const char *__restrict __fmt, ...)
>    return __dprintf_chk (__fd, __USE_FORTIFY_LEVEL - 1, __fmt,
>  			__va_arg_pack ());
>  }
> +#  elif __fortify_use_clang
> +__fortify_function_error_function __attribute_overloadable__ int
> +dprintf (int __fd, __fortify_clang_overload_arg (const char *, __restrict,
> +						 __fmt), ...)
> +{
> +  __gnuc_va_list __fortify_ap;
> +  __builtin_va_start (__fortify_ap, __fmt);
> +  int __r = __vdprintf_chk (__fd, __USE_FORTIFY_LEVEL - 1, __fmt,
> +			    __fortify_ap);
> +  __builtin_va_end (__fortify_ap);
> +  return __r;
> +}
>  #  elif !defined __cplusplus
>  #   define dprintf(fd, ...) \
>    __dprintf_chk (fd, __USE_FORTIFY_LEVEL - 1, __VA_ARGS__)
> @@ -153,6 +222,43 @@ __NTH (obstack_printf (struct obstack *__restrict __obstack,
>    return __obstack_printf_chk (__obstack, __USE_FORTIFY_LEVEL - 1, __fmt,
>  			       __va_arg_pack ());
>  }
> +#  elif __fortify_use_clang
> +__fortify_function_error_function __attribute_overloadable__ int
> +__NTH (asprintf (__fortify_clang_overload_arg (char **, __restrict, __ptr),
> +		 const char *__restrict __fmt, ...))
> +{
> +  __gnuc_va_list __fortify_ap;
> +  __builtin_va_start (__fortify_ap, __fmt);
> +  int __r = __vasprintf_chk (__ptr, __USE_FORTIFY_LEVEL - 1, __fmt,
> +			     __fortify_ap);
> +  __builtin_va_end (__fortify_ap);
> +  return __r;
> +}
> +
> +__fortify_function_error_function __attribute_overloadable__ int
> +__NTH (__asprintf (__fortify_clang_overload_arg (char **, __restrict, __ptr),
> +		   const char *__restrict __fmt, ...))
> +{
> +  __gnuc_va_list __fortify_ap;
> +  __builtin_va_start (__fortify_ap, __fmt);
> +  int __r = __vasprintf_chk (__ptr, __USE_FORTIFY_LEVEL - 1, __fmt,
> +			     __fortify_ap);
> +  __builtin_va_end (__fortify_ap);
> +  return __r;
> +}
> +
> +__fortify_function_error_function __attribute_overloadable__ int
> +__NTH (obstack_printf (__fortify_clang_overload_arg (struct obstack *,
> +						     __restrict, __obstack),
> +		       const char *__restrict __fmt, ...))
> +{
> +  __gnuc_va_list __fortify_ap;
> +  __builtin_va_start (__fortify_ap, __fmt);
> +  int __r = __obstack_vprintf_chk (__obstack, __USE_FORTIFY_LEVEL - 1,
> +				   __fmt, __fortify_ap);
> +  __builtin_va_end (__fortify_ap);
> +  return __r;
> +}
>  #  elif !defined __cplusplus
>  #   define asprintf(ptr, ...) \
>    __asprintf_chk (ptr, __USE_FORTIFY_LEVEL - 1, __VA_ARGS__)
> @@ -182,8 +288,11 @@ __NTH (obstack_vprintf (struct obstack *__restrict __obstack,
>  #endif
>  
>  #if __GLIBC_USE (DEPRECATED_GETS)
> -__fortify_function __wur char *
> -gets (char *__str)
> +__fortify_function __wur __attribute_overloadable__ char *
> +gets (__fortify_clang_overload_arg (char *, , __str))
> +     __fortify_clang_warning (__glibc_objsize (__str) == (size_t) -1,
> +			      "please use fgets or getline instead, gets "
> +			      "can not specify buffer size")
>  {
>    if (__glibc_objsize (__str) != (size_t) -1)
>      return __gets_chk (__str, __glibc_objsize (__str));
> @@ -192,48 +301,70 @@ gets (char *__str)
>  #endif
>  
>  __fortify_function __wur __fortified_attr_access (__write_only__, 1, 2)
> -__nonnull ((3)) char *
> -fgets (char *__restrict __s, int __n, FILE *__restrict __stream)
> +__nonnull ((3)) __attribute_overloadable__ char *
> +fgets (__fortify_clang_overload_arg (char *, __restrict, __s), int __n,
> +       FILE *__restrict __stream)
> +     __fortify_clang_warning (__fortify_clang_bos_static_lt (__n, __s) && __n > 0,
> +			      "fgets called with bigger size than length of "
> +			      "destination buffer")
>  {
>    size_t sz = __glibc_objsize (__s);
>    if (__glibc_safe_or_unknown_len (__n, sizeof (char), sz))
>      return __fgets_alias (__s, __n, __stream);
> +#if !__fortify_use_clang
>    if (__glibc_unsafe_len (__n, sizeof (char), sz))
>      return __fgets_chk_warn (__s, sz, __n, __stream);
> +#endif
>    return __fgets_chk (__s, sz, __n, __stream);
>  }
>  
> -__fortify_function __wur __nonnull ((4)) size_t
> -fread (void *__restrict __ptr, size_t __size, size_t __n,
> -       FILE *__restrict __stream)
> +__fortify_function __wur __nonnull ((4)) __attribute_overloadable__ size_t
> +fread (__fortify_clang_overload_arg (void *, __restrict, __ptr),
> +       size_t __size, size_t __n, FILE *__restrict __stream)
> +     __fortify_clang_warning (__fortify_clang_bos0_static_lt (__size * __n, __ptr)
> +			      && !__fortify_clang_mul_may_overflow (__size, __n),
> +			      "fread called with bigger size * n than length "
> +			      "of destination buffer")
>  {
>    size_t sz = __glibc_objsize0 (__ptr);
>    if (__glibc_safe_or_unknown_len (__n, __size, sz))
>      return __fread_alias (__ptr, __size, __n, __stream);
> +#if !__fortify_use_clang
>    if (__glibc_unsafe_len (__n, __size, sz))
>      return __fread_chk_warn (__ptr, sz, __size, __n, __stream);
> +#endif
>    return __fread_chk (__ptr, sz, __size, __n, __stream);
>  }
>  
>  #ifdef __USE_GNU
>  __fortify_function __wur __fortified_attr_access (__write_only__, 1, 2)
> -__nonnull ((3)) char *
> -fgets_unlocked (char *__restrict __s, int __n, FILE *__restrict __stream)
> +__nonnull ((3)) __attribute_overloadable__ char *
> +fgets_unlocked (__fortify_clang_overload_arg (char *, __restrict, __s),
> +		int __n, FILE *__restrict __stream)
> +     __fortify_clang_warning (__fortify_clang_bos_static_lt (__n, __s) && __n > 0,
> +			      "fgets called with bigger size than length of "
> +			      "destination buffer")
>  {
>    size_t sz = __glibc_objsize (__s);
>    if (__glibc_safe_or_unknown_len (__n, sizeof (char), sz))
>      return __fgets_unlocked_alias (__s, __n, __stream);
> +#if !__fortify_use_clang
>    if (__glibc_unsafe_len (__n, sizeof (char), sz))
>      return __fgets_unlocked_chk_warn (__s, sz, __n, __stream);
> +#endif

OK. Interesting difference here.

>    return __fgets_unlocked_chk (__s, sz, __n, __stream);
>  }
>  #endif
>  
>  #ifdef __USE_MISC
>  # undef fread_unlocked
> -__fortify_function __wur __nonnull ((4)) size_t
> -fread_unlocked (void *__restrict __ptr, size_t __size, size_t __n,
> -		FILE *__restrict __stream)
> +__fortify_function __wur __nonnull ((4)) __attribute_overloadable__ size_t
> +fread_unlocked (__fortify_clang_overload_arg0 (void *, __restrict, __ptr),
> +		size_t __size, size_t __n, FILE *__restrict __stream)
> +     __fortify_clang_warning (__fortify_clang_bos0_static_lt (__size * __n, __ptr)
> +			      && !__fortify_clang_mul_may_overflow (__size, __n),
> +			      "fread_unlocked called with bigger size * n than "
> +			      "length of destination buffer")
>  {
>    size_t sz = __glibc_objsize0 (__ptr);
>    if (__glibc_safe_or_unknown_len (__n, __size, sz))
> @@ -261,8 +392,10 @@ fread_unlocked (void *__restrict __ptr, size_t __size, size_t __n,
>  # endif
>        return __fread_unlocked_alias (__ptr, __size, __n, __stream);
>      }
> +# if !__fortify_use_clang
>    if (__glibc_unsafe_len (__n, __size, sz))
>      return __fread_unlocked_chk_warn (__ptr, sz, __size, __n, __stream);
> +# endif

OK.

>    return __fread_unlocked_chk (__ptr, sz, __size, __n, __stream);
>  
>  }
  

On 20/02/24 19:06, Carlos O'Donell wrote:
> On 2/8/24 13:46, Adhemerval Zanella wrote:
>> It improve fortify checks for sprintf, vsprintf, vsnsprintf, fprintf,
>> dprintf, asprintf, __asprintf, obstack_printf, gets, fgets,
>> fgets_unlocked, fread, and fread_unlocked.  The runtime checks have
>> similar support coverage as with GCC.
> 
> LGTM.
> 
> Tested on x86_64 and i686 with gcc.
> 
> Reviewed-by: Carlos O'Donell <carlos@redhat.com>
> Tested-by: Carlos O'Donell <carlos@redhat.com>
> 
>> For function with variadic argument (sprintf, snprintf, fprintf, printf,
>> dprintf, asprintf, __asprintf, obstack_printf) the fortify wrapper calls
>> the va_arg version since clang does not support __va_arg_pack.
>>
>> Checked on aarch64, armhf, x86_64, and i686.
>> ---
>>  libio/bits/stdio2.h | 173 +++++++++++++++++++++++++++++++++++++++-----
>>  1 file changed, 153 insertions(+), 20 deletions(-)
>>
>> diff --git a/libio/bits/stdio2.h b/libio/bits/stdio2.h
>> index f9e8d37610..91a80dd7c6 100644
>> --- a/libio/bits/stdio2.h
>> +++ b/libio/bits/stdio2.h
>> @@ -31,15 +31,29 @@ __NTH (sprintf (char *__restrict __s, const char *__restrict __fmt, ...))
>>  				  __glibc_objsize (__s), __fmt,
>>  				  __va_arg_pack ());
>>  }
>> +#elif __fortify_use_clang
>> +/* clang does not have __va_arg_pack, so defer to va_arg version.  */
>> +__fortify_function_error_function __attribute_overloadable__ int
>> +__NTH (sprintf (__fortify_clang_overload_arg (char *, __restrict, __s),
>> +		const char *__restrict __fmt, ...))
>> +{
>> +  __gnuc_va_list __fortify_ap;
>> +  __builtin_va_start (__fortify_ap, __fmt);
>> +  int __r = __builtin___vsprintf_chk (__s, __USE_FORTIFY_LEVEL - 1,
>> +				      __glibc_objsize (__s), __fmt,
>> +				      __fortify_ap);
>> +  __builtin_va_end (__fortify_ap);
>> +  return __r;
>> +}
>>  #elif !defined __cplusplus
>>  # define sprintf(str, ...) \
>>    __builtin___sprintf_chk (str, __USE_FORTIFY_LEVEL - 1,		      \
>>  			   __glibc_objsize (str), __VA_ARGS__)
>>  #endif
>>  
>> -__fortify_function int
>> -__NTH (vsprintf (char *__restrict __s, const char *__restrict __fmt,
>> -		 __gnuc_va_list __ap))
>> +__fortify_function __attribute_overloadable__ int
>> +__NTH (vsprintf (__fortify_clang_overload_arg (char *, __restrict, __s),
>> +		 const char *__restrict __fmt, __gnuc_va_list __ap))
>>  {
>>    return __builtin___vsprintf_chk (__s, __USE_FORTIFY_LEVEL - 1,
>>  				   __glibc_objsize (__s), __fmt, __ap);
>> @@ -55,15 +69,33 @@ __NTH (snprintf (char *__restrict __s, size_t __n,
>>  				   __glibc_objsize (__s), __fmt,
>>  				   __va_arg_pack ());
>>  }
>> +# elif __fortify_use_clang
>> +/* clang does not have __va_arg_pack, so defer to va_arg version.  */
>> +__fortify_function_error_function __attribute_overloadable__ int
>> +__NTH (snprintf (__fortify_clang_overload_arg (char *, __restrict, __s),
>> +		 size_t __n, const char *__restrict __fmt, ...))
>> +{
>> +  __gnuc_va_list __fortify_ap;
>> +  __builtin_va_start (__fortify_ap, __fmt);
>> +  int __r = __builtin___vsnprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
>> +				       __glibc_objsize (__s), __fmt,
>> +				       __fortify_ap);
>> +  __builtin_va_end (__fortify_ap);
>> +  return __r;
>> +}
>>  # elif !defined __cplusplus
>>  #  define snprintf(str, len, ...) \
>>    __builtin___snprintf_chk (str, len, __USE_FORTIFY_LEVEL - 1,		      \
>>  			    __glibc_objsize (str), __VA_ARGS__)
>>  # endif
>>  
>> -__fortify_function int
>> -__NTH (vsnprintf (char *__restrict __s, size_t __n,
>> -		  const char *__restrict __fmt, __gnuc_va_list __ap))
>> +__fortify_function __attribute_overloadable__ int
>> +__NTH (vsnprintf (__fortify_clang_overload_arg (char *, __restrict, __s),
>> +		  size_t __n, const char *__restrict __fmt,
>> +		  __gnuc_va_list __ap))
>> +     __fortify_clang_warning (__fortify_clang_bos_static_lt (__n, __s),
>> +			      "call to vsnprintf may overflow the destination "
>> +			      "buffer")
> 
> OK.
> 
>>  {
>>    return __builtin___vsnprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
>>  				    __glibc_objsize (__s), __fmt, __ap);
>> @@ -85,6 +117,30 @@ printf (const char *__restrict __fmt, ...)
>>  {
>>    return __printf_chk (__USE_FORTIFY_LEVEL - 1, __fmt, __va_arg_pack ());
>>  }
>> +# elif __fortify_use_clang
>> +/* clang does not have __va_arg_pack, so defer to va_arg version.  */
>> +__fortify_function_error_function __attribute_overloadable__ __nonnull ((1)) int
>> +fprintf (__fortify_clang_overload_arg (FILE *, __restrict, __stream),
>> +	 const char *__restrict __fmt, ...)
>> +{
>> +  __gnuc_va_list __fortify_ap;
>> +  __builtin_va_start (__fortify_ap, __fmt);
>> +  int __r = __builtin___vfprintf_chk (__stream, __USE_FORTIFY_LEVEL - 1,
>> +				      __fmt, __fortify_ap);
>> +  __builtin_va_end (__fortify_ap);
>> +  return __r;
>> +}
>> +
>> +__fortify_function_error_function __attribute_overloadable__ int
>> +printf (__fortify_clang_overload_arg (const char *, __restrict, __fmt), ...)
>> +{
>> +  __gnuc_va_list __fortify_ap;
>> +  __builtin_va_start (__fortify_ap, __fmt);
>> +  int __r = __builtin___vprintf_chk (__USE_FORTIFY_LEVEL - 1, __fmt,
>> +				     __fortify_ap);
>> +  __builtin_va_end (__fortify_ap);
>> +  return __r;
>> +}
>>  # elif !defined __cplusplus
>>  #  define printf(...) \
>>    __printf_chk (__USE_FORTIFY_LEVEL - 1, __VA_ARGS__)
>> @@ -92,8 +148,9 @@ printf (const char *__restrict __fmt, ...)
>>    __fprintf_chk (stream, __USE_FORTIFY_LEVEL - 1, __VA_ARGS__)
>>  # endif
>>  
>> -__fortify_function int
>> -vprintf (const char *__restrict __fmt, __gnuc_va_list __ap)
>> +__fortify_function __attribute_overloadable__ int
>> +vprintf (__fortify_clang_overload_arg (const char *, __restrict, __fmt),
>> +	 __gnuc_va_list __ap)
>>  {
>>  #ifdef __USE_EXTERN_INLINES
>>    return __vfprintf_chk (stdout, __USE_FORTIFY_LEVEL - 1, __fmt, __ap);
>> @@ -117,6 +174,18 @@ dprintf (int __fd, const char *__restrict __fmt, ...)
>>    return __dprintf_chk (__fd, __USE_FORTIFY_LEVEL - 1, __fmt,
>>  			__va_arg_pack ());
>>  }
>> +#  elif __fortify_use_clang
>> +__fortify_function_error_function __attribute_overloadable__ int
>> +dprintf (int __fd, __fortify_clang_overload_arg (const char *, __restrict,
>> +						 __fmt), ...)
>> +{
>> +  __gnuc_va_list __fortify_ap;
>> +  __builtin_va_start (__fortify_ap, __fmt);
>> +  int __r = __vdprintf_chk (__fd, __USE_FORTIFY_LEVEL - 1, __fmt,
>> +			    __fortify_ap);
>> +  __builtin_va_end (__fortify_ap);
>> +  return __r;
>> +}
>>  #  elif !defined __cplusplus
>>  #   define dprintf(fd, ...) \
>>    __dprintf_chk (fd, __USE_FORTIFY_LEVEL - 1, __VA_ARGS__)
>> @@ -153,6 +222,43 @@ __NTH (obstack_printf (struct obstack *__restrict __obstack,
>>    return __obstack_printf_chk (__obstack, __USE_FORTIFY_LEVEL - 1, __fmt,
>>  			       __va_arg_pack ());
>>  }
>> +#  elif __fortify_use_clang
>> +__fortify_function_error_function __attribute_overloadable__ int
>> +__NTH (asprintf (__fortify_clang_overload_arg (char **, __restrict, __ptr),
>> +		 const char *__restrict __fmt, ...))
>> +{
>> +  __gnuc_va_list __fortify_ap;
>> +  __builtin_va_start (__fortify_ap, __fmt);
>> +  int __r = __vasprintf_chk (__ptr, __USE_FORTIFY_LEVEL - 1, __fmt,
>> +			     __fortify_ap);
>> +  __builtin_va_end (__fortify_ap);
>> +  return __r;
>> +}
>> +
>> +__fortify_function_error_function __attribute_overloadable__ int
>> +__NTH (__asprintf (__fortify_clang_overload_arg (char **, __restrict, __ptr),
>> +		   const char *__restrict __fmt, ...))
>> +{
>> +  __gnuc_va_list __fortify_ap;
>> +  __builtin_va_start (__fortify_ap, __fmt);
>> +  int __r = __vasprintf_chk (__ptr, __USE_FORTIFY_LEVEL - 1, __fmt,
>> +			     __fortify_ap);
>> +  __builtin_va_end (__fortify_ap);
>> +  return __r;
>> +}
>> +
>> +__fortify_function_error_function __attribute_overloadable__ int
>> +__NTH (obstack_printf (__fortify_clang_overload_arg (struct obstack *,
>> +						     __restrict, __obstack),
>> +		       const char *__restrict __fmt, ...))
>> +{
>> +  __gnuc_va_list __fortify_ap;
>> +  __builtin_va_start (__fortify_ap, __fmt);
>> +  int __r = __obstack_vprintf_chk (__obstack, __USE_FORTIFY_LEVEL - 1,
>> +				   __fmt, __fortify_ap);
>> +  __builtin_va_end (__fortify_ap);
>> +  return __r;
>> +}
>>  #  elif !defined __cplusplus
>>  #   define asprintf(ptr, ...) \
>>    __asprintf_chk (ptr, __USE_FORTIFY_LEVEL - 1, __VA_ARGS__)
>> @@ -182,8 +288,11 @@ __NTH (obstack_vprintf (struct obstack *__restrict __obstack,
>>  #endif
>>  
>>  #if __GLIBC_USE (DEPRECATED_GETS)
>> -__fortify_function __wur char *
>> -gets (char *__str)
>> +__fortify_function __wur __attribute_overloadable__ char *
>> +gets (__fortify_clang_overload_arg (char *, , __str))
>> +     __fortify_clang_warning (__glibc_objsize (__str) == (size_t) -1,
>> +			      "please use fgets or getline instead, gets "
>> +			      "can not specify buffer size")
>>  {
>>    if (__glibc_objsize (__str) != (size_t) -1)
>>      return __gets_chk (__str, __glibc_objsize (__str));
>> @@ -192,48 +301,70 @@ gets (char *__str)
>>  #endif
>>  
>>  __fortify_function __wur __fortified_attr_access (__write_only__, 1, 2)
>> -__nonnull ((3)) char *
>> -fgets (char *__restrict __s, int __n, FILE *__restrict __stream)
>> +__nonnull ((3)) __attribute_overloadable__ char *
>> +fgets (__fortify_clang_overload_arg (char *, __restrict, __s), int __n,
>> +       FILE *__restrict __stream)
>> +     __fortify_clang_warning (__fortify_clang_bos_static_lt (__n, __s) && __n > 0,
>> +			      "fgets called with bigger size than length of "
>> +			      "destination buffer")
>>  {
>>    size_t sz = __glibc_objsize (__s);
>>    if (__glibc_safe_or_unknown_len (__n, sizeof (char), sz))
>>      return __fgets_alias (__s, __n, __stream);
>> +#if !__fortify_use_clang
>>    if (__glibc_unsafe_len (__n, sizeof (char), sz))
>>      return __fgets_chk_warn (__s, sz, __n, __stream);
>> +#endif
>>    return __fgets_chk (__s, sz, __n, __stream);
>>  }
>>  
>> -__fortify_function __wur __nonnull ((4)) size_t
>> -fread (void *__restrict __ptr, size_t __size, size_t __n,
>> -       FILE *__restrict __stream)
>> +__fortify_function __wur __nonnull ((4)) __attribute_overloadable__ size_t
>> +fread (__fortify_clang_overload_arg (void *, __restrict, __ptr),
>> +       size_t __size, size_t __n, FILE *__restrict __stream)
>> +     __fortify_clang_warning (__fortify_clang_bos0_static_lt (__size * __n, __ptr)
>> +			      && !__fortify_clang_mul_may_overflow (__size, __n),
>> +			      "fread called with bigger size * n than length "
>> +			      "of destination buffer")
>>  {
>>    size_t sz = __glibc_objsize0 (__ptr);
>>    if (__glibc_safe_or_unknown_len (__n, __size, sz))
>>      return __fread_alias (__ptr, __size, __n, __stream);
>> +#if !__fortify_use_clang
>>    if (__glibc_unsafe_len (__n, __size, sz))
>>      return __fread_chk_warn (__ptr, sz, __size, __n, __stream);
>> +#endif
>>    return __fread_chk (__ptr, sz, __size, __n, __stream);
>>  }
>>  
>>  #ifdef __USE_GNU
>>  __fortify_function __wur __fortified_attr_access (__write_only__, 1, 2)
>> -__nonnull ((3)) char *
>> -fgets_unlocked (char *__restrict __s, int __n, FILE *__restrict __stream)
>> +__nonnull ((3)) __attribute_overloadable__ char *
>> +fgets_unlocked (__fortify_clang_overload_arg (char *, __restrict, __s),
>> +		int __n, FILE *__restrict __stream)
>> +     __fortify_clang_warning (__fortify_clang_bos_static_lt (__n, __s) && __n > 0,
>> +			      "fgets called with bigger size than length of "
>> +			      "destination buffer")
>>  {
>>    size_t sz = __glibc_objsize (__s);
>>    if (__glibc_safe_or_unknown_len (__n, sizeof (char), sz))
>>      return __fgets_unlocked_alias (__s, __n, __stream);
>> +#if !__fortify_use_clang
>>    if (__glibc_unsafe_len (__n, sizeof (char), sz))
>>      return __fgets_unlocked_chk_warn (__s, sz, __n, __stream);
>> +#endif
> 
> OK. Interesting difference here.
> 

Yeah, the __diagnose_if__ attribute, along with the '__fortify_clang_bos_static_lt
[...]' already provide the same diagnostic (in fact this is essentially one the
main differences of the fortify implementation between gcc and clang).

>>    return __fgets_unlocked_chk (__s, sz, __n, __stream);
>>  }
>>  #endif
>>  
>>  #ifdef __USE_MISC
>>  # undef fread_unlocked
>> -__fortify_function __wur __nonnull ((4)) size_t
>> -fread_unlocked (void *__restrict __ptr, size_t __size, size_t __n,
>> -		FILE *__restrict __stream)
>> +__fortify_function __wur __nonnull ((4)) __attribute_overloadable__ size_t
>> +fread_unlocked (__fortify_clang_overload_arg0 (void *, __restrict, __ptr),
>> +		size_t __size, size_t __n, FILE *__restrict __stream)
>> +     __fortify_clang_warning (__fortify_clang_bos0_static_lt (__size * __n, __ptr)
>> +			      && !__fortify_clang_mul_may_overflow (__size, __n),
>> +			      "fread_unlocked called with bigger size * n than "
>> +			      "length of destination buffer")
>>  {
>>    size_t sz = __glibc_objsize0 (__ptr);
>>    if (__glibc_safe_or_unknown_len (__n, __size, sz))
>> @@ -261,8 +392,10 @@ fread_unlocked (void *__restrict __ptr, size_t __size, size_t __n,
>>  # endif
>>        return __fread_unlocked_alias (__ptr, __size, __n, __stream);
>>      }
>> +# if !__fortify_use_clang
>>    if (__glibc_unsafe_len (__n, __size, sz))
>>      return __fread_unlocked_chk_warn (__ptr, sz, __size, __n, __stream);
>> +# endif
> 
> OK.
> 
>>    return __fread_unlocked_chk (__ptr, sz, __size, __n, __stream);
>>  
>>  }
>