Learn English – Is this usage of “however” with an adjective correct

You can actually say "The program erred at line 44", but it's not very idiomatic. "Err" also occurs in the saying "To err is human, to forgive is divine".

If you're looking for the correct idiom, you could say "the program encountered an error at line 44" or "the program hit an error at line 44", etc.

The Old English word lang has suffix forms -ling and -long, (“with the direction, duration, or length”), similar to -lic (“with the body or form”) that survives as the very common -ly adverbial suffix form.

The -ling form, once used in words like hinderling (“in the backward direction”) has been supplanted by another usage, the nominal diminutive: darling, yearling. The -long form still survives, with all three senses, in words like headlong, nightlong, and footlong.

The suffix is adverbial in directional modifiers like headlong and arselong, adjectival in metric modifiers like footlong and nightlong. When combined with a quantifier to form an adjectival or adverbial phrase, the metrics compounds break into their component words:

• I ate a footlong sandwich. [adjective]
• This sandwich is one foot long. [adjectival phrase]
• This sandwich measures one foot long. [adverbial phrase]
• We attended a nightlong party. [adjective]
• We stayed at the party the whole night long. [adverbial phrase]

As these express spatial and temporal dimension rather than relationship, it's not clear whether these are adpositions or simply adjectives with an idiomatic phrase order. However, the close similarity to a hole one foot through or party the whole night through suggests that they may indeed be postpositions.