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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
compiler/evalffi.nim
View file

@ -65,16 +65,16 @@ proc importcSymbol*(conf: ConfigRef, sym: PSym): PNode =
if (lib.isNil or lib.kind == libHeader) and not gExeHandle.isNil:
libPathMsg = "current exe: " & getAppFilename() & " nor libc: " & libcDll
# first try this exe itself:
theAddr = gExeHandle.symAddr(name)
theAddr = gExeHandle.symAddr(name.cstring)
# then try libc:
if theAddr.isNil:
let dllhandle = getDll(conf, gDllCache, libcDll, sym.info)
theAddr = dllhandle.symAddr(name)
theAddr = dllhandle.symAddr(name.cstring)
elif not lib.isNil:
let dll = if lib.kind == libHeader: libcDll else: lib.path.strVal
libPathMsg = dll
let dllhandle = getDll(conf, gDllCache, dll, sym.info)
theAddr = dllhandle.symAddr(name)
theAddr = dllhandle.symAddr(name.cstring)
if theAddr.isNil: globalError(conf, sym.info,
"cannot import symbol: " & name & " from " & libPathMsg)
result.intVal = cast[ByteAddress](theAddr)

8
compiler/tccgen.nim
View file

@ -48,15 +48,15 @@ proc setupEnvironment =
var tinycRoot = nimDir / tinyPrefix
let libpath = nimDir / "lib"
addIncludePath(gTinyC, libpath)
addIncludePath(gTinyC, cstring(libpath))
when defined(windows):
addSysincludePath(gTinyC, tinycRoot / "tinyc/win32/include")
addSysincludePath(gTinyC, tinycRoot / "tinyc/include")
addSysincludePath(gTinyC, cstring(tinycRoot / "tinyc/win32/include"))
addSysincludePath(gTinyC, cstring(tinycRoot / "tinyc/include"))
when defined(windows):
defineSymbol(gTinyC, "_WIN32", nil)
# we need Mingw's headers too:
var gccbin = getConfigVar("gcc.path") % ["nim", tinycRoot]
addSysincludePath(gTinyC, gccbin /../ "include")
addSysincludePath(gTinyC, cstring(gccbin /../ "include"))
#addFile(tinycRoot / r"tinyc\win32\wincrt1.o")
addFile(tinycRoot / r"tinyc\win32\alloca86.o")
addFile(tinycRoot / r"tinyc\win32\chkstk.o")