Make serd_strtod API const-correct

This is an API breakage, but a minor one (particularly since NULL is
allowed) that avoids the flaw in the C API.

1 files changed, 4 insertions, 2 deletions

diff --git a/tests/serd_test.c b/tests/serd_test.c
index d41bbfc1..4a1c2485 100644
--- a/tests/serd_test.c
+++ b/tests/serd_test.c
@@ -39,11 +39,13 @@ test_strtod(double dbl, double max_delta)
 	char buf[1024];
 	snprintf(buf, sizeof(buf), "%f", dbl);
 
-	char* endptr = NULL;
-	const double out = serd_strtod(buf, &endptr);
+	size_t       end = 0;
+	const double out = serd_strtod(buf, &end);
 
 	const double diff = fabs(out - dbl);
 	assert(diff <= max_delta);
+	assert(end == strlen(buf));
+
 	return 0;
 }