[PATCH 3/5] config: set errno in numeric git_parse_* functions

[Jeff King <peff@xxxxxxxx>]

When we are parsing an integer or unsigned long, we use
the strto*max functions, which properly set errno to ERANGE
if we get a large value. However, we also do further range
checks after applying our multiplication factor, but do not
set ERANGE. This means that a caller cannot tell if an error
was caused by ERANGE or if the input was simply not a valid
number.

This patch teaches git_parse_signed and git_parse_unsigned
reliably set ERANGE for range errors, and EINVAL for other
errors.

Signed-off-by: Jeff King <peff@xxxxxxxx>
---
I'm a little iffy on using errno like this. The "normal" way in git
would be to return an enum like:

  enum config_parse_error {
    CONFIG_PARSE_SUCCESS = 0,
    CONFIG_PARSE_RANGE = -1,
    CONFIG_PARSE_INVALID_UNIT = -2
  };

But that would be changing the return semantics of git_parse_ulong
(which currently is "0" for fail, "1" for success) without changing its
signature. I figured this was the path of least resistance since we
already get ERANGE out of strtoimax, but I'm happy to switch it, too.

 config.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/config.c b/config.c
index 0a65ac2..7332b06 100644
--- a/config.c
+++ b/config.c
@@ -480,16 +480,21 @@ static int git_parse_signed(const char *value, intmax_t *ret, intmax_t max)
 		val = strtoimax(value, &end, 0);
 		if (errno == ERANGE)
 			return 0;
-		if (!parse_unit_factor(end, &factor))
+		if (!parse_unit_factor(end, &factor)) {
+			errno = EINVAL;
 			return 0;
+		}
 		uval = abs(val);
 		uval *= factor;
-		if (uval > max || abs(val) > uval)
+		if (uval > max || abs(val) > uval) {
+			errno = ERANGE;
 			return 0;
+		}
 		val *= factor;
 		*ret = val;
 		return 1;
 	}
+	errno = EINVAL;
 	return 0;
 }
 
@@ -505,13 +510,18 @@ int git_parse_unsigned(const char *value, uintmax_t *ret, uintmax_t max)
 		if (errno == ERANGE)
 			return 0;
 		oldval = val;
-		if (!parse_unit_factor(end, &val))
+		if (!parse_unit_factor(end, &val)) {
+			errno = EINVAL;
 			return 0;
-		if (val > max || oldval > val)
+		}
+		if (val > max || oldval > val) {
+			errno = ERANGE;
 			return 0;
+		}
 		*ret = val;
 		return 1;
 	}
+	errno = EINVAL;
 	return 0;
 }
 
-- 
1.8.4.2.g87d4a77

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