C2x scanf binary constant handling

C2x adds binary integer constants starting with 0b or 0B, and supports
those constants for the %i scanf format (in addition to the %b format,
which isn't yet implemented for scanf in glibc).  Implement that scanf
support for glibc.

As with the strtol support, this is incompatible with previous C
standard versions, in that such an input string starting with 0b or 0B
was previously required to be parsed as 0 (with the rest of the input
potentially matching subsequent parts of the scanf format string).
Thus this patch adds 12 new __isoc23_* functions per long double
format (12, 24 or 36 depending on how many long double formats the
glibc configuration supports), with appropriate header redirection
support (generally very closely following that for the __isoc99_*
scanf functions - note that __GLIBC_USE (DEPRECATED_SCANF) takes
precedence over __GLIBC_USE (C2X_STRTOL), so the case of GNU
extensions to C89 continues to get old-style GNU %a and does not get
this new feature).  The function names would remain as __isoc23_* even
if C2x ends up published in 2024 rather than 2023.

When scanf %b support is added, I think it will be appropriate for all
versions of scanf to follow C2x rules for inputs to the %b format
(given that there are no compatibility concerns for a new format).

Tested for x86_64 (full glibc testsuite).  The first version was also
tested for powerpc (32-bit) and powerpc64le (stdio-common/ and wcsmbs/
tests), and with build-many-glibcs.py.

3 files changed, 92 insertions, 11 deletions

diff --git a/libio/bits/stdio-ldbl.h b/libio/bits/stdio-ldbl.h
index b54d00b..ed68fc4 100644
--- a/libio/bits/stdio-ldbl.h
+++ b/libio/bits/stdio-ldbl.h
@@ -28,13 +28,25 @@ __LDBL_REDIR_DECL (vprintf)
 __LDBL_REDIR_DECL (vsprintf)
 #if !__GLIBC_USE (DEPRECATED_SCANF)
 # if defined __LDBL_COMPAT
+#  if __GLIBC_USE (C2X_STRTOL)
+__LDBL_REDIR1_DECL (fscanf, __nldbl___isoc23_fscanf)
+__LDBL_REDIR1_DECL (scanf, __nldbl___isoc23_scanf)
+__LDBL_REDIR1_DECL (sscanf, __nldbl___isoc23_sscanf)
+#  else
 __LDBL_REDIR1_DECL (fscanf, __nldbl___isoc99_fscanf)
 __LDBL_REDIR1_DECL (scanf, __nldbl___isoc99_scanf)
 __LDBL_REDIR1_DECL (sscanf, __nldbl___isoc99_sscanf)
+#  endif
 # elif __LDOUBLE_REDIRECTS_TO_FLOAT128_ABI == 1
+#  if __GLIBC_USE (C2X_STRTOL)
+__LDBL_REDIR1_DECL (fscanf, __isoc23_fscanfieee128)
+__LDBL_REDIR1_DECL (scanf, __isoc23_scanfieee128)
+__LDBL_REDIR1_DECL (sscanf, __isoc23_sscanfieee128)
+#  else
 __LDBL_REDIR1_DECL (fscanf, __isoc99_fscanfieee128)
 __LDBL_REDIR1_DECL (scanf, __isoc99_scanfieee128)
 __LDBL_REDIR1_DECL (sscanf, __isoc99_sscanfieee128)
+#  endif
 # else
 #  error bits/stdlib-ldbl.h included when no ldbl redirections are required.
 # endif
@@ -52,13 +64,25 @@ __LDBL_REDIR_DECL (vsnprintf)
 #ifdef	__USE_ISOC99
 # if !__GLIBC_USE (DEPRECATED_SCANF)
 #  if defined __LDBL_COMPAT
+#   if __GLIBC_USE (C2X_STRTOL)
+__LDBL_REDIR1_DECL (vfscanf, __nldbl___isoc23_vfscanf)
+__LDBL_REDIR1_DECL (vscanf, __nldbl___isoc23_vscanf)
+__LDBL_REDIR1_DECL (vsscanf, __nldbl___isoc23_vsscanf)
+#   else
 __LDBL_REDIR1_DECL (vfscanf, __nldbl___isoc99_vfscanf)
 __LDBL_REDIR1_DECL (vscanf, __nldbl___isoc99_vscanf)
 __LDBL_REDIR1_DECL (vsscanf, __nldbl___isoc99_vsscanf)
+#   endif
 #  elif __LDOUBLE_REDIRECTS_TO_FLOAT128_ABI == 1
+#   if __GLIBC_USE (C2X_STRTOL)
+__LDBL_REDIR1_DECL (vfscanf, __isoc23_vfscanfieee128)
+__LDBL_REDIR1_DECL (vscanf, __isoc23_vscanfieee128)
+__LDBL_REDIR1_DECL (vsscanf, __isoc23_vsscanfieee128)
+#   else
 __LDBL_REDIR1_DECL (vfscanf, __isoc99_vfscanfieee128)
 __LDBL_REDIR1_DECL (vscanf, __isoc99_vscanfieee128)
 __LDBL_REDIR1_DECL (vsscanf, __isoc99_vsscanfieee128)
+#   endif
 #  else
 #   error bits/stdlib-ldbl.h included when no ldbl redirections are required.
 #  endif
diff --git a/libio/libioP.h b/libio/libioP.h
index a5f0082..3850738 100644
--- a/libio/libioP.h
+++ b/libio/libioP.h
@@ -781,6 +781,9 @@ extern off64_t _IO_seekpos_unlocked (FILE *, off64_t, int)
    functions use.  When the flag is set to zero, automatic allocation is
    enabled.
 
+   SCANF_ISOC23_BIN_CST, when set to one, indicates the %i accepts
+   binary constants starting 0b or 0B.
+
    SCANF_LDBL_USES_FLOAT128 is used on platforms where the long double
    format used to be different from the IEC 60559 double format *and*
    also different from the Quadruple 128-bits IEC 60559 format (such as
@@ -793,7 +796,8 @@ extern off64_t _IO_seekpos_unlocked (FILE *, off64_t, int)
    as the previous format on that platform.  */
 #define SCANF_LDBL_IS_DBL		0x0001
 #define SCANF_ISOC99_A			0x0002
-#define SCANF_LDBL_USES_FLOAT128	0x0004
+#define SCANF_ISOC23_BIN_CST		0x0004
+#define SCANF_LDBL_USES_FLOAT128	0x0008
 
 extern int __vfscanf_internal (FILE *fp, const char *format, va_list argp,
 			       unsigned int flags)
diff --git a/libio/stdio.h b/libio/stdio.h
index ed80420..857f028 100644
--- a/libio/stdio.h
+++ b/libio/stdio.h
@@ -430,7 +430,28 @@ extern int sscanf (const char *__restrict __s,
 #include <bits/floatn.h>
 #if !__GLIBC_USE (DEPRECATED_SCANF) && !defined __LDBL_COMPAT \
     && __LDOUBLE_REDIRECTS_TO_FLOAT128_ABI == 0
-# ifdef __REDIRECT
+# if __GLIBC_USE (C2X_STRTOL)
+#  ifdef __REDIRECT
+extern int __REDIRECT (fscanf, (FILE *__restrict __stream,
+				const char *__restrict __format, ...),
+		       __isoc23_fscanf) __wur;
+extern int __REDIRECT (scanf, (const char *__restrict __format, ...),
+		       __isoc23_scanf) __wur;
+extern int __REDIRECT_NTH (sscanf, (const char *__restrict __s,
+				    const char *__restrict __format, ...),
+			   __isoc23_sscanf);
+#  else
+extern int __isoc23_fscanf (FILE *__restrict __stream,
+			    const char *__restrict __format, ...) __wur;
+extern int __isoc23_scanf (const char *__restrict __format, ...) __wur;
+extern int __isoc23_sscanf (const char *__restrict __s,
+			    const char *__restrict __format, ...) __THROW;
+#   define fscanf __isoc23_fscanf
+#   define scanf __isoc23_scanf
+#   define sscanf __isoc23_sscanf
+#  endif
+# else
+#  ifdef __REDIRECT
 extern int __REDIRECT (fscanf, (FILE *__restrict __stream,
 				const char *__restrict __format, ...),
 		       __isoc99_fscanf) __wur;
@@ -439,15 +460,16 @@ extern int __REDIRECT (scanf, (const char *__restrict __format, ...),
 extern int __REDIRECT_NTH (sscanf, (const char *__restrict __s,
 				    const char *__restrict __format, ...),
 			   __isoc99_sscanf);
-# else
+#  else
 extern int __isoc99_fscanf (FILE *__restrict __stream,
 			    const char *__restrict __format, ...) __wur;
 extern int __isoc99_scanf (const char *__restrict __format, ...) __wur;
 extern int __isoc99_sscanf (const char *__restrict __s,
 			    const char *__restrict __format, ...) __THROW;
-#  define fscanf __isoc99_fscanf
-#  define scanf __isoc99_scanf
-#  define sscanf __isoc99_sscanf
+#   define fscanf __isoc99_fscanf
+#   define scanf __isoc99_scanf
+#   define sscanf __isoc99_sscanf
+#  endif
 # endif
 #endif
 
@@ -474,7 +496,37 @@ extern int vsscanf (const char *__restrict __s,
 
 /* Same redirection as above for the v*scanf family.  */
 # if !__GLIBC_USE (DEPRECATED_SCANF)
-#  if defined __REDIRECT && !defined __LDBL_COMPAT \
+#  if __GLIBC_USE (C2X_STRTOL)
+#   if defined __REDIRECT && !defined __LDBL_COMPAT	\
+      && __LDOUBLE_REDIRECTS_TO_FLOAT128_ABI == 0
+extern int __REDIRECT (vfscanf,
+		       (FILE *__restrict __s,
+			const char *__restrict __format, __gnuc_va_list __arg),
+		       __isoc23_vfscanf)
+     __attribute__ ((__format__ (__scanf__, 2, 0))) __wur;
+extern int __REDIRECT (vscanf, (const char *__restrict __format,
+				__gnuc_va_list __arg), __isoc23_vscanf)
+     __attribute__ ((__format__ (__scanf__, 1, 0))) __wur;
+extern int __REDIRECT_NTH (vsscanf,
+			   (const char *__restrict __s,
+			    const char *__restrict __format,
+			    __gnuc_va_list __arg), __isoc23_vsscanf)
+     __attribute__ ((__format__ (__scanf__, 2, 0)));
+#   elif !defined __REDIRECT
+extern int __isoc23_vfscanf (FILE *__restrict __s,
+			     const char *__restrict __format,
+			     __gnuc_va_list __arg) __wur;
+extern int __isoc23_vscanf (const char *__restrict __format,
+			    __gnuc_va_list __arg) __wur;
+extern int __isoc23_vsscanf (const char *__restrict __s,
+			     const char *__restrict __format,
+			     __gnuc_va_list __arg) __THROW;
+#    define vfscanf __isoc23_vfscanf
+#    define vscanf __isoc23_vscanf
+#    define vsscanf __isoc23_vsscanf
+#   endif
+#  else
+#   if defined __REDIRECT && !defined __LDBL_COMPAT	\
       && __LDOUBLE_REDIRECTS_TO_FLOAT128_ABI == 0
 extern int __REDIRECT (vfscanf,
 		       (FILE *__restrict __s,
@@ -489,7 +541,7 @@ extern int __REDIRECT_NTH (vsscanf,
 			    const char *__restrict __format,
 			    __gnuc_va_list __arg), __isoc99_vsscanf)
      __attribute__ ((__format__ (__scanf__, 2, 0)));
-#  elif !defined __REDIRECT
+#   elif !defined __REDIRECT
 extern int __isoc99_vfscanf (FILE *__restrict __s,
 			     const char *__restrict __format,
 			     __gnuc_va_list __arg) __wur;
@@ -498,9 +550,10 @@ extern int __isoc99_vscanf (const char *__restrict __format,
 extern int __isoc99_vsscanf (const char *__restrict __s,
 			     const char *__restrict __format,
 			     __gnuc_va_list __arg) __THROW;
-#   define vfscanf __isoc99_vfscanf
-#   define vscanf __isoc99_vscanf
-#   define vsscanf __isoc99_vsscanf
+#    define vfscanf __isoc99_vfscanf
+#    define vscanf __isoc99_vscanf
+#    define vsscanf __isoc99_vsscanf
+#   endif
 #  endif
 # endif
 #endif /* Use ISO C9x.  */