manual: documents changes regarding dynlib (#13425)

* manual: documents changes regarding dynlib

Closes #13416

* manual: clean up sentence phrasing

changelog.md

@@ -32,7 +32,9 @@
 - Implicit conversions for `const` behave correctly now, meaning that code like
   `const SOMECONST = 0.int; procThatTakesInt32(SOMECONST)` will be illegal now.
   Simply write `const SOMECONST = 0` instead.
-
+- The `{.dynlib.}` pragma is now required for exporting symbols when making
+  shared objects on POSIX and macOS, which make it consistent with the behavior
+  on Windows.
 
 
 ## Library additions

doc/manual.rst

@@ -7224,6 +7224,9 @@ The string literal passed to ``exportc`` can be a format string:
 In the example the external name of ``p`` is set to ``prefixp``. Only ``$1``
 is available and a literal dollar sign must be written as ``$$``.
 
+If the symbol should also be exported to a dynamic library, the ``dynlib``
+pragma should be used in addition to the ``exportc`` pragma. See
+`Dynlib pragma for export <#foreign-function-interface-dynlib-pragma-for-export>`_.
 
 
 Extern pragma
@@ -7363,10 +7366,7 @@ conjunction with the ``exportc`` pragma:
   proc exportme(): int {.cdecl, exportc, dynlib.}
 
 This is only useful if the program is compiled as a dynamic library via the
-``--app:lib`` command line option. This pragma only has an effect for the code
-generation on the Windows target, so when this pragma is forgotten and the dynamic
-library is only tested on Mac and/or Linux, there won't be an error. On Windows
-this pragma adds ``__declspec(dllexport)`` to the function declaration.
+``--app:lib`` command line option.