Import official C23 code examples for Modern C (Jens Gustedt, 2024)HEADupstream-importmain

- Add official C source files, Makefile, c23-fallback.h, and LICENSE
- Update README.md with study mirror notice

1 files changed, 48 insertions, 0 deletions

diff --git a/bitint.c b/bitint.c
new file mode 100644
index 0000000..bf2b559
--- /dev/null
+++ b/bitint.c
@@ -0,0 +1,48 @@
+#include <stdio.h>
+#include "c23-fallback.h"
+
+#ifndef BITINT_MAXWIDTH
+# error "no _BitInt support found, aborting compilation"
+// shut off some subsequent error messages
+# include "no _BitInt support found, aborting compilation"
+#endif
+
+int main (int argc, char* argv[static argc+1]) {
+  // this doesn't fit, diagnose?
+  _BitInt(15)          s15 = 0b1010101'01010101wb;
+  unsigned _BitInt(15) u15 = 0b1010101'01010101wbu;
+  // this doesn't fit, diagnose?
+  _BitInt(15) su15 = u15;
+
+  auto u65 = 0x1'FFFF'FFFF'FFFF'FFFFwbu;
+  // wrap around arithmetic is fine.
+  auto oa65 = 0x1'FFFF'FFFF'FFFF'FFFFwbu + 1wbu;
+  // constant too wide, diagnostic?
+  typeof(u65) o65 = 0x2'FFFF'FFFF'FFFF'FFFFwbu;
+
+  auto s65 = 0xFFFF'FFFF'FFFF'FFFFwb;
+  // signed arithmetic overflows, diagnostic?
+  auto sa65 = 0xFFFF'FFFF'FFFF'FFFFwb + 1wb;
+  // constant too wide, diagnostic?
+  typeof(s65) os65 = 0x1'FFFF'FFFF'FFFF'FFFFwb;
+
+  unsigned _BitInt(128) max128s = 0x7FFF'FFFF'FFFF'FFFF'FFFF'FFFF'FFFF'FFFFwb;
+  unsigned _BitInt(128) min128s = -1wb -max128s;
+
+  unsigned _BitInt(3) max3u = -1;
+  unsigned _BitInt(4) max4u = -1;
+  unsigned _BitInt(4) one4u = max4u - max3u;
+    signed _BitInt(4) max4s = max3u;
+    signed _BitInt(4) min4s = ~max4s;
+
+  printf("15 bits, signed:\t%d\n", (signed)s15);
+  printf("15 bits, unsigned:\t%u\n", (unsigned)u15);
+  printf("15 bits, u → s:\t%d\n", (signed)su15);
+  printf("4 bits:\t%u\n", (unsigned)max4u);
+  printf("4 bits:\t%u\n", (unsigned)one4u);
+  printf("4 bits:\t%d\n", (signed)max4s);
+  printf("4 bits:\t%d\n", (signed)min4s);
+  printf("4 bit arithm:\t%u\n", (unsigned)(max4u + 1wbu));
+  printf("int arithm:\t%u\n", (unsigned)(max4u + 1));
+  return s15 + su15 + u15 + u65 + oa65 + o65 + s65 + sa65 + os65 + !max128s + !min128s;
+}