From a3eb2381f2a48457765fb4b96e72b1591bbf9051 Mon Sep 17 00:00:00 2001
From: ee7 <45465154+ee7@users.noreply.github.com>
Date: Fri, 19 Aug 2022 21:40:53 +0200
Subject: [PATCH] make implicit cstring conversions explicit (#19488)

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] https://github.com/nim-lang/Nim/blob/d2318d9ccfe6/doc/manual.md#cstring-type
[2] https://github.com/nim-lang/Nim/blob/d2318d9ccfe6/changelogs/changelog_1_6_0.md#type-system
---
 src/db_odbc.nim | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/db_odbc.nim b/src/db_odbc.nim
index 1e4032b348..0ecd8129f1 100644
--- a/src/db_odbc.nim
+++ b/src/db_odbc.nim
@@ -334,7 +334,7 @@ proc `[]`*(row: InstantRow, col: int): string {.inline.} =
 
 proc unsafeColumnAt*(row: InstantRow, index: int): cstring {.inline.} =
   ## Return cstring of given column of the row
-  row.row[index]
+  row.row[index].cstring
 
 proc len*(row: InstantRow): int {.inline.} =
   ## Returns number of columns in the row