URL scheme validation does not correctly implement RFC 3986

[ad0p]

I am trying to use curl_url_set to validate a string and check whether it's a valid URL. I use option CURLU_NON_SUPPORT_SCHEME as I need to support custom schemes.

In urlapi.c, there is the following comment:

  /* RFC 3986 3.1 explains:
    scheme      = ALPHA *( ALPHA / DIGIT / "+" / "-" / "." )
  */

But actual implementation is more like:

    scheme      =  1*( ALPHA / DIGIT / "+" / "-" / "." )

I have tested that the following examples are marked by libcurl curl_url_set as valid:

• 1h://example1
• ..://example2
• -://example3
  -+://example4

Those are not valid URLs according to RFC 3986 3.1, but libcurl treats them as valid ones.