[PATCH] stdio: make scanf(%f) eat the same number of characters as strtod() would

[Joseph Myers]

On Wed, 1 Jan 2025, Miklós Máté wrote:

> According to the spec the %f conversion specifier (and its synonyms) must
> behave exactly as strtod(). This behavior matches FreeBSD libc. On MSVC

No, scanf should read a string that is *or is a prefix of* a matching 
string.  (Footnote 330 in C23 says "fscanf pushes back at most one input 
character onto the input stream. Therefore, some sequences that are 
acceptable to strtod, strtol, etc., are unacceptable to fscanf.".)  If 
it's a prefix but not a matching sequence, that is a matching failure.  
See bug 12701 and duplicates (18246 is probably a duplicate though not 
currently marked as such).

If you're interested in working in this area, talk to Maciej first since 
he's working on scanf testing.

-- 
Joseph S. Myers
josmyers@redhat.com