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net: internal dtoi and xtoi helpers have unusual API #16350

mdempsky opened this issue Jul 13, 2016 · 3 comments


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commented Jul 13, 2016

These internal helpers have signatures like:

func dtoi(s string, i0 int) ...
func xtoi(s string, i0 int) ...

and they parse an integer value from &s[i0]. Especially since the majority of callers use i0==0, it seems like it would be simpler / more idiomatic to just have the caller pass s[i0:] as an argument.

In particular, dtoi theoretically supports parsing negative integers, except it looks for the '-' character at s[0], not s[i0].

/cc @bradfitz @dpiddy

@mdempsky mdempsky added this to the Go1.8 milestone Jul 13, 2016


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commented Jul 13, 2016

Yes, those weird me out every time I encounter them.


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commented Aug 17, 2016

CL mentions this issue.

@gopherbot gopherbot closed this in 00b779a Aug 17, 2016


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commented Sep 2, 2016

CL mentions this issue.

gopherbot pushed a commit that referenced this issue Sep 7, 2016

net: remove parsing of negative decimals in IPv4 literal fixed the dtoi function such that
it now properly parses negative number. Ironically, this causes
several other functions that depended on dtoi to now (incorrectly)
parse negative numbers.

For example, ParseCIDR("-") used to be rejected prior to the
above CL, but is now accepted even though it is an invalid CIDR notation.
This CL fixes that regression.

We fix this by removing the signed parsing logic entirely from dtoi.
It was introduced relatively recently in
to fix a bug where an invalid port was improperly being parsed as OK.
It seems to me that the fix in that CL to the port handling logic was
sufficient such that a change to dtoi was unnecessary.

Updates #16350

Change-Id: I414bb1aa27d0a226ebd4b05a09cb40d784691b43
Reviewed-by: Matthew Dempsky <>
Reviewed-by: Mikio Hara <>
Run-TryBot: Joe Tsai <>

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