[musl] [C23 scanf 1/3] C23: Add the b specifier for scanf and allow 0b and 0B prefixes in integers

[Jens Gustedt <Jens.Gustedt@inria.fr>]

This affects all functions that read integers from strings or streams
such as scanf and strtoX.

This patch changes the behavior deep down inside, namely the __intscan
function. This is a semantic change. Parsing of integers that use base
0 (for the strtoX functions) or the "i" specifier (for scanf) may
observe different behavior when linked (statically or dynamically)
against this new version.

The C committtee did explicitly reject concerns about this
incompatibility, judging it as being only a minor risk.
---
 src/internal/intscan.c | 13 +++++++++++--
 src/stdio/vfscanf.c    |  5 ++++-
 src/stdio/vfwscanf.c   |  4 ++--
 3 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/src/internal/intscan.c b/src/internal/intscan.c
index a4a5ae86..57424554 100644
--- a/src/internal/intscan.c
+++ b/src/internal/intscan.c
@@ -38,9 +38,9 @@ unsigned long long __intscan(FILE *f, unsigned base, int pok, unsigned long long
 		neg = -(c=='-');
 		c = shgetc(f);
 	}
-	if ((base == 0 || base == 16) && c=='0') {
+	if ((base == 0 || base == 2 || base == 16) && c=='0') {
 		c = shgetc(f);
-		if ((c|32)=='x') {
+		if ((c|32)=='x' && base != 2) {
 			c = shgetc(f);
 			if (val[c]>=16) {
 				shunget(f);
@@ -49,6 +49,15 @@ unsigned long long __intscan(FILE *f, unsigned base, int pok, unsigned long long
 				return 0;
 			}
 			base = 16;
+		} else if ((c|32)=='b' && base != 16) {
+			c = shgetc(f);
+			if (val[c]>=2) {
+				shunget(f);
+				if (pok) shunget(f);
+				else shlim(f, 0);
+				return 0;
+			}
+			base = 2;
 		} else if (base == 0) {
 			base = 8;
 		}
diff --git a/src/stdio/vfscanf.c b/src/stdio/vfscanf.c
index b78a374d..f72ac9c9 100644
--- a/src/stdio/vfscanf.c
+++ b/src/stdio/vfscanf.c
@@ -150,7 +150,7 @@ int vfscanf(FILE *restrict f, const char *restrict fmt, va_list ap)
 		case 'L':
 			size = SIZE_L;
 			break;
-		case 'd': case 'i': case 'o': case 'u': case 'x':
+		case 'b': case 'd': case 'i': case 'o': case 'u': case 'x':
 		case 'a': case 'e': case 'f': case 'g':
 		case 'A': case 'E': case 'F': case 'G': case 'X':
 		case 's': case 'c': case '[':
@@ -286,6 +286,9 @@ int vfscanf(FILE *restrict f, const char *restrict fmt, va_list ap)
 		case 'o':
 			base = 8;
 			goto int_common;
+		case 'b':
+			base = 2;
+			goto int_common;
 		case 'd':
 		case 'u':
 			base = 10;
diff --git a/src/stdio/vfwscanf.c b/src/stdio/vfwscanf.c
index 82f48604..17f5a2f9 100644
--- a/src/stdio/vfwscanf.c
+++ b/src/stdio/vfwscanf.c
@@ -173,7 +173,7 @@ int vfwscanf(FILE *restrict f, const wchar_t *restrict fmt, va_list ap)
 		case 'L':
 			size = SIZE_L;
 			break;
-		case 'd': case 'i': case 'o': case 'u': case 'x':
+		case 'b': case 'd': case 'i': case 'o': case 'u': case 'x':
 		case 'a': case 'e': case 'f': case 'g':
 		case 'A': case 'E': case 'F': case 'G': case 'X':
 		case 's': case 'c': case '[':
@@ -294,7 +294,7 @@ int vfwscanf(FILE *restrict f, const wchar_t *restrict fmt, va_list ap)
 			}
 			break;
 
-		case 'd': case 'i': case 'o': case 'u': case 'x':
+		case 'b': case 'd': case 'i': case 'o': case 'u': case 'x':
 		case 'a': case 'e': case 'f': case 'g':
 		case 'A': case 'E': case 'F': case 'G': case 'X':
 		case 'p':
-- 
2.34.1