1 files changed, 85 insertions, 0 deletions
diff --git a/src/port/strtof.c b/src/port/strtof.c
new file mode 100644
index 0000000..fea45a8
--- /dev/null
+++ b/src/port/strtof.c
@@ -0,0 +1,85 @@
+/*-------------------------------------------------------------------------
+ *
+ * strtof.c
+ *
+ * Portions Copyright (c) 2019-2023, PostgreSQL Global Development Group
+ *
+ *
+ * IDENTIFICATION
+ *	  src/port/strtof.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "c.h"
+
+#include <float.h>
+#include <math.h>
+
+
+/*
+ * Cygwin has a strtof() which is literally just (float)strtod(), which means
+ * we can't avoid the double-rounding problem; but using this wrapper does get
+ * us proper over/underflow checks. (Also, if they fix their strtof(), the
+ * wrapper doesn't break anything.)
+ *
+ * Test results on Mingw suggest that it has the same problem, though looking
+ * at the code I can't figure out why.
+ */
+float
+pg_strtof(const char *nptr, char **endptr)
+{
+	int			caller_errno = errno;
+	float		fresult;
+
+	errno = 0;
+	fresult = (strtof) (nptr, endptr);
+	if (errno)
+	{
+		/* On error, just return the error to the caller. */
+		return fresult;
+	}
+	else if ((*endptr == nptr) || isnan(fresult) ||
+			 ((fresult >= FLT_MIN || fresult <= -FLT_MIN) && !isinf(fresult)))
+	{
+		/*
+		 * If we got nothing parseable, or if we got a non-0 non-subnormal
+		 * finite value (or NaN) without error, then return that to the caller
+		 * without error.
+		 */
+		errno = caller_errno;
+		return fresult;
+	}
+	else
+	{
+		/*
+		 * Try again. errno is already 0 here.
+		 */
+		double		dresult = strtod(nptr, NULL);
+
+		if (errno)
+		{
+			/* On error, just return the error */
+			return fresult;
+		}
+		else if ((dresult == 0.0 && fresult == 0.0) ||
+				 (isinf(dresult) && isinf(fresult) && (fresult == dresult)))
+		{
+			/* both values are 0 or infinities of the same sign */
+			errno = caller_errno;
+			return fresult;
+		}
+		else if ((dresult > 0 && dresult <= FLT_MIN && (float) dresult != 0.0) ||
+				 (dresult < 0 && dresult >= -FLT_MIN && (float) dresult != 0.0))
+		{
+			/* subnormal but nonzero value */
+			errno = caller_errno;
+			return (float) dresult;
+		}
+		else
+		{
+			errno = ERANGE;
+			return fresult;
+		}
+	}
+}