cras_string: Check for error before setting value

In parse_float and parse_double, finish checking the errno values first
before setting the parsed value.

BUG=b:320231979
TEST=Unit tests

Change-Id: I658e50bfd33b9efbc727f6e300eed70efea29278
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/adhd/+/5233200
Tested-by: Baili Deng <bailideng@google.com>
Reviewed-by: Li-Yu Yu <aaronyu@google.com>
Commit-Queue: Curtis Malainey <cujomalainey@chromium.org>
Auto-Submit: Baili Deng <bailideng@google.com>
Reviewed-by: Curtis Malainey <cujomalainey@chromium.org>
Tested-by: chromeos-cop-builder@chromeos-cop.iam.gserviceaccount.com <chromeos-cop-builder@chromeos-cop.iam.gserviceaccount.com>

cras/src/common/cras_string.h

@@ -58,10 +58,11 @@ static __attribute__((warn_unused_result)) inline int parse_float(
   }
   char* endptr;
   errno = 0;
-  *out = strtof(str, &endptr);
+  float f = strtof(str, &endptr);
   if (endptr == str) {
     return -EINVAL;
   }
+  *out = f;
   return -errno;
 }
 
@@ -74,10 +75,11 @@ static __attribute__((warn_unused_result)) inline int parse_double(
   }
   char* endptr;
   errno = 0;
-  *out = strtod(str, &endptr);
+  double d = strtod(str, &endptr);
   if (endptr == str) {
     return -EINVAL;
   }
+  *out = d;
   return -errno;
 }