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make implicit cstring conversions explicit (#19488)

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The Nim manual says that an implicit conversion to cstring will
eventually not be allowed [1]:

    A Nim `string` is implicitly convertible to `cstring` for convenience.

    [...]

    Even though the conversion is implicit, it is not *safe*: The garbage collector
    does not consider a `cstring` to be a root and may collect the underlying
    memory. For this reason, the implicit conversion will be removed in future
    releases of the Nim compiler. Certain idioms like conversion of a `const` string
    to `cstring` are safe and will remain to be allowed.

And from Nim 1.6.0, such a conversion triggers a warning [2]:

    A dangerous implicit conversion to `cstring` now triggers a `[CStringConv]` warning.
    This warning will become an error in future versions! Use an explicit conversion
    like `cstring(x)` in order to silence the warning.

However, some files in this repo produced such a warning. For example,
before this commit, compiling `parsejson.nim` would produce:

    /foo/Nim/lib/pure/parsejson.nim(221, 37) Warning: implicit conversion to 'cstring' from a non-const location: my.buf; this will become a compile time error in the future [CStringConv]
    /foo/Nim/lib/pure/parsejson.nim(231, 39) Warning: implicit conversion to 'cstring' from a non-const location: my.buf; this will become a compile time error in the future [CStringConv]

This commit resolves the most visible `CStringConv` warnings, making the
cstring conversions explicit.

[1] d2318d9ccf/doc/manual.md (cstring-type)
[2] d2318d9ccf/changelogs/changelog_1_6_0.md (type-system)
This commit is contained in:
ee7 2022-08-19 21:40:53 +02:00 • committed by GitHub
commit e8657c7107
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14 changed files with 63 additions and 63 deletions
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6
lib/pure/nativesockets.nim
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@ -300,7 +300,7 @@ proc getAddrInfo*(address: string, port: Port, domain: Domain = AF_INET,
if domain == AF_INET6:
hints.ai_flags = AI_V4MAPPED
let socketPort = if sockType == SOCK_RAW: "" else: $port
var gaiResult = getaddrinfo(address, socketPort, addr(hints), result)
var gaiResult = getaddrinfo(address, socketPort.cstring, addr(hints), result)
if gaiResult != 0'i32:
when useWinVersion or defined(freertos):
raiseOSError(osLastError())
@ -460,10 +460,10 @@ when not useNimNetLite:
const size = 256
result = newString(size)
when useWinVersion:
let success = winlean.gethostname(result, size)
let success = winlean.gethostname(result.cstring, size)
else:
# Posix
let success = posix.gethostname(result, size)
let success = posix.gethostname(result.cstring, size)
if success != 0.cint:
raiseOSError(osLastError())
let x = len(cstring(result))