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misc bugfixes [backport:1.2] #19203

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Dec 4, 2021
Merged

misc bugfixes [backport:1.2] #19203

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6 changes: 3 additions & 3 deletions compiler/semobjconstr.nim
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Original file line number Diff line number Diff line change
Expand Up @@ -366,9 +366,9 @@ proc defaultConstructionError(c: PContext, t: PType, info: TLineInfo) =
if objType.kind == tyObject:
var constrCtx = initConstrContext(objType, newNodeI(nkObjConstr, info))
let initResult = semConstructTypeAux(c, constrCtx, {})
assert constrCtx.missingFields.len > 0
localError(c.config, info,
"The $1 type doesn't have a default value. The following fields must be initialized: $2." % [typeToString(t), listSymbolNames(constrCtx.missingFields)])
if constrCtx.missingFields.len > 0:
localError(c.config, info,
"The $1 type doesn't have a default value. The following fields must be initialized: $2." % [typeToString(t), listSymbolNames(constrCtx.missingFields)])
Comment on lines +369 to +371
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It might be useful to add a test case for this.

elif objType.kind == tyDistinct:
localError(c.config, info,
"The $1 distinct type doesn't have a default value." % typeToString(t))
Expand Down
23 changes: 9 additions & 14 deletions doc/backends.rst
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Expand Up @@ -52,7 +52,7 @@ The commands to compile to either C, C++ or Objective-C are:
The most significant difference between these commands is that if you look
into the ``nimcache`` directory you will find ``.c``, ``.cpp`` or ``.m``
files, other than that all of them will produce a native binary for your
project. This allows you to take the generated code and place it directly
project. This allows you to take the generated code and place it directly
into a project using any of these languages. Here are some typical command-
line invocations:

Expand Down Expand Up @@ -123,7 +123,7 @@ Nim code can interface with the backend through the `Foreign function
interface <manual.html#foreign-function-interface>`_ mainly through the
`importc pragma <manual.html#foreign-function-interface-importc-pragma>`_.
The `importc` pragma is the *generic* way of making backend symbols available
in Nim and is available in all the target backends (JavaScript too). The C++
in Nim and is available in all the target backends (JavaScript too). The C++
or Objective-C backends have their respective `ImportCpp
<manual.html#implementation-specific-pragmas-importcpp-pragma>`_ and
`ImportObjC <manual.html#implementation-specific-pragmas-importobjc-pragma>`_
Expand Down Expand Up @@ -246,11 +246,6 @@ Also, C code requires you to specify a forward declaration for functions or
the compiler will assume certain types for the return value and parameters
which will likely make your program crash at runtime.

The Nim compiler can generate a C interface header through the `--header`:option:
command-line switch. The generated header will contain all the exported
symbols and the `NimMain` proc which you need to call before any other
Nim code.


Nim invocation example from C
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Expand All @@ -269,9 +264,10 @@ Create a ``maths.c`` file with the following content:

.. code-block:: c

#include "fib.h"
#include <stdio.h>

extern int fib(int a);

int main(void)
{
NimMain();
Expand All @@ -286,13 +282,12 @@ program:

.. code:: cmd

nim c --noMain --noLinking --header:fib.h fib.nim
nim c --noMain --noLinking fib.nim
gcc -o m -I$HOME/.cache/nim/fib_d -Ipath/to/nim/lib $HOME/.cache/nim/fib_d/*.c maths.c

The first command runs the Nim compiler with three special options to avoid
generating a `main()`:c: function in the generated files, avoid linking the
object files into a final binary, and explicitly generate a header file for C
integration. All the generated files are placed into the ``nimcache``
generating a `main()`:c: function in the generated files and to avoid linking the
object files into a final binary. All the generated files are placed into the ``nimcache``
directory. That's why the next command compiles the ``maths.c`` source plus
all the ``.c`` files from ``nimcache``. In addition to this path, you also
have to tell the C compiler where to find Nim's ``nimbase.h`` header file.
Expand All @@ -302,12 +297,12 @@ also ask the Nim compiler to generate a statically linked library:

.. code:: cmd

nim c --app:staticLib --noMain --header fib.nim
nim c --app:staticLib --noMain fib.nim
gcc -o m -Inimcache -Ipath/to/nim/lib libfib.nim.a maths.c

The Nim compiler will handle linking the source files generated in the
``nimcache`` directory into the ``libfib.nim.a`` static library, which you can
then link into your C program. Note that these commands are generic and will
then link into your C program. Note that these commands are generic and will
vary for each system. For instance, on Linux systems you will likely need to
use `-ldl`:option: too to link in required dlopen functionality.

Expand Down