build: fix various shared library build issues

Node.js unofficially supports a shared library variant where the
main node executable is a thin wrapper around node.dll/libnode.so.
The key benefit of this is to support embedding Node.js in other
applications.

Since Node.js 12 there have been a number of issues preventing the
shared library build from working correctly, primarily on Windows:

* A number of functions used executables such as `mksnapshot` are
    not exported from `libnode.dll` using a `NODE_EXTERN` attribute
* A dependency on the `Winmm` system library is missing
* Incorrect defines on executable targets leads to `node.exe`
    claiming to export a number of functions that are actually in
    `libnode.dll`
* Because `node.exe` attempts to export symbols, `node.lib` gets
    generated causing native extensions to try to link against
    `node.exe` not `libnode.dll`.
* Similarly, because `node.dll` was renamed to `libnode.dll`,
    native extensions don't know to look for `libnode.lib` rather
    than `node.lib`.
* On macOS an RPATH is added to find `libnode.dylib` relative to
    `node` in the same folder. This works fine from the
    `out/Release` folder but not from an installed prefix, where
    `node` will be in `bin/` and `libnode.dylib` will be in `lib/`.
* Similarly on Linux, no RPATH is added so LD_LIBRARY_PATH needs
    setting correctly for `bin/node` to find `lib/libnode.so`.

For the `libnode.lib` vs `node.lib` issue there are two possible
options:

1. Ensure `node.lib` from `node.exe` does not get generated, and
    instead copy `libnode.lib` to `node.lib`. This means addons
    compiled when referencing the correct `node.lib` file will
    correctly depend on `libnode.dll`. The down side is that
    native addons compiled with stock Node.js will still try to
    resolve symbols against node.exe rather than libnode.dll.
2. After building `libnode.dll`, dump the exports using `dumpbin`,
    and process this to generate a `node.def` file to be linked into
    `node.exe` with the `/DEF:node.def` flag. The export entries
    in `node.def` will all read
    ```
    my_symbol=libnode.my_symbol
    ```
    so that `node.exe` will redirect all exported symbols back to
    `libnode.dll`. This has the benefit that addons compiled with
    stock Node.js will load correctly into `node.exe` from a shared
    library build, but means that every embedding executable also
    needs to perform this same trick.

I went with the first option as it is the cleaner of the two
solutions in my opinion. Projects wishing to generate a shared
library variant of Node.js can now, for example,
```
.\vcbuild dll package vs
```
to generate a full node installation including `libnode.dll`,
`Release\node.lib`, and all the necessary headers. Native addons
can then be built against the shared library build easily by
specifying the correct `nodedir` option.

For example
```
>npx node-gyp configure --nodedir
   C:\Users\User\node\Release\node-v18.0.0-win-x64
...
>npx node-gyp build
...
>dumpbin /dependents build\Release\binding.node
Microsoft (R) COFF/PE Dumper Version 14.29.30136.0
Copyright (C) Microsoft Corporation.  All rights reserved.

Dump of file build\Release\binding.node

File Type: DLL

  Image has the following dependencies:

    KERNEL32.dll
    libnode.dll
    VCRUNTIME140.dll
    api-ms-win-crt-string-l1-1-0.dll
    api-ms-win-crt-stdio-l1-1-0.dll
    api-ms-win-crt-runtime-l1-1-0.dll
...
```

PR-URL: https://github.com/nodejs/node/pull/41850
Reviewed-By: Michael Dawson <midawson@redhat.com>
Reviewed-By: Beth Griggs <bgriggs@redhat.com>
Reviewed-By: Richard Lau <rlau@redhat.com>

1 files changed, 54 insertions, 1 deletions

diff --git a/node.gyp b/node.gyp
index 4e06d00c823..e2a7cd5d69d 100644
--- a/node.gyp
+++ b/node.gyp
@@ -196,6 +196,16 @@
           'dependencies': [ 'node_aix_shared' ],
         }, {
           'dependencies': [ '<(node_lib_target_name)' ],
+          'conditions': [
+            ['OS=="win" and node_shared=="true"', {
+              'dependencies': ['generate_node_def'],
+              'msvs_settings': {
+                'VCLinkerTool': {
+                  'ModuleDefinitionFile': '<(PRODUCT_DIR)/<(node_core_target_name).def',
+                },
+              },
+            }],
+          ],
         }],
         [ 'node_intermediate_lib_type=="static_library" and node_shared=="false"', {
           'xcode_settings': {
@@ -235,8 +245,15 @@
         }],
         [ 'node_shared=="true"', {
           'xcode_settings': {
-            'OTHER_LDFLAGS': [ '-Wl,-rpath,@loader_path', ],
+            'OTHER_LDFLAGS': [ '-Wl,-rpath,@loader_path', '-Wl,-rpath,@loader_path/../lib'],
           },
+          'conditions': [
+            ['OS=="linux"', {
+               'ldflags': [
+                 '-Wl,-rpath,\\$$ORIGIN/../lib'
+               ],
+            }],
+          ],
         }],
         [ 'enable_lto=="true"', {
           'xcode_settings': {
@@ -749,6 +766,7 @@
           'libraries': [
             'Dbghelp',
             'Psapi',
+            'Winmm',
             'Ws2_32',
           ],
         }],
@@ -1502,5 +1520,40 @@
         },
       ]
     }], # end aix section
+    ['OS=="win" and node_shared=="true"', {
+     'targets': [
+       {
+         'target_name': 'gen_node_def',
+         'type': 'executable',
+         'sources': [
+           'tools/gen_node_def.cc'
+         ],
+       },
+       {
+         'target_name': 'generate_node_def',
+         'dependencies': [
+           'gen_node_def',
+           '<(node_lib_target_name)',
+         ],
+         'type': 'none',
+         'actions': [
+           {
+             'action_name': 'generate_node_def_action',
+             'inputs': [
+               '<(PRODUCT_DIR)/<(node_lib_target_name).dll'
+             ],
+             'outputs': [
+               '<(PRODUCT_DIR)/<(node_core_target_name).def',
+             ],
+             'action': [
+               '<(PRODUCT_DIR)/gen_node_def.exe',
+               '<@(_inputs)',
+               '<@(_outputs)',
+             ],
+           },
+         ],
+       },
+     ],
+   }], # end win section
   ], # end conditions block
 }