Merge pull request #6688 from dcbaker/emcc-linker-bugs

Emcc linker bugs and improvments

docs/markdown/Builtin-options.md

@@ -151,20 +151,22 @@ The following options are available. Note that both the options themselves and
 the possible values they can take will depend on the target platform or
 compiler being used:
 
-| Option       | Default value | Possible values                          | Description |
-| ------       | ------------- | ---------------                          | ----------- |
-| c_args       |               | free-form comma-separated list           | C compile arguments to use |
-| c_link_args  |               | free-form comma-separated list           | C link arguments to use |
-| c_std        | none          | none, c89, c99, c11, c17, c18, gnu89, gnu99, gnu11, gnu17, gnu18 | C language standard to use |
-| c_winlibs    | see below     | free-form comma-separated list           | Standard Windows libs to link against |
-| cpp_args     |               | free-form comma-separated list           | C++ compile arguments to use |
-| cpp_link_args|               | free-form comma-separated list           | C++ link arguments to use |
-| cpp_std      | none          | none, c++98, c++03, c++11, c++14, c++17, <br/>c++1z, gnu++03, gnu++11, gnu++14, gnu++17, gnu++1z, <br/> vc++14, vc++17, vc++latest | C++ language standard to use |
-| cpp_debugstl | false         | true, false                              | C++ STL debug mode |
-| cpp_eh       | default       | none, default, a, s, sc                  | C++ exception handling type |
-| cpp_rtti     | true          | true, false                              | Whether to enable RTTI (runtime type identification) |
-| cpp_winlibs  | see below     | free-form comma-separated list           | Standard Windows libs to link against |
-| fortran_std  | none          | [none, legacy, f95, f2003, f2008, f2018] | Fortran language standard to use |
+| Option           | Default value | Possible values                          | Description |
+| ------           | ------------- | ---------------                          | ----------- |
+| c_args           |               | free-form comma-separated list           | C compile arguments to use |
+| c_link_args      |               | free-form comma-separated list           | C link arguments to use |
+| c_std            | none          | none, c89, c99, c11, c17, c18, gnu89, gnu99, gnu11, gnu17, gnu18 | C language standard to use |
+| c_winlibs        | see below     | free-form comma-separated list           | Standard Windows libs to link against |
+| c_thread_count   | 4             | integer value ≥ 0                        | Number of threads to use with emcc when using threads |
+| cpp_args         |               | free-form comma-separated list           | C++ compile arguments to use |
+| cpp_link_args    |               | free-form comma-separated list           | C++ link arguments to use |
+| cpp_std          | none          | none, c++98, c++03, c++11, c++14, c++17, <br/>c++1z, gnu++03, gnu++11, gnu++14, gnu++17, gnu++1z, <br/> vc++14, vc++17, vc++latest | C++ language standard to use |
+| cpp_debugstl     | false         | true, false                              | C++ STL debug mode |
+| cpp_eh           | default       | none, default, a, s, sc                  | C++ exception handling type |
+| cpp_rtti         | true          | true, false                              | Whether to enable RTTI (runtime type identification) |
+| cpp_thread_count | 4             | integer value ≥ 0                        | Number of threads to use with emcc when using threads |
+| cpp_winlibs      | see below     | free-form comma-separated list           | Standard Windows libs to link against |
+| fortran_std      | none          | [none, legacy, f95, f2003, f2008, f2018] | Fortran language standard to use |
 
 The default values of `c_winlibs` and `cpp_winlibs` are in compiler-specific
 argument forms, but the libraries are: kernel32, user32, gdi32, winspool,
@@ -179,3 +181,7 @@ while the `cpp_eh=[value]` will result in `/EH[value]`.
 Since *0.51.0* `cpp_eh=default` will result in `/EHsc` on MSVC. When using
 gcc-style compilers, nothing is passed (allowing exceptions to work), while
 `cpp_eh=none` passes `-fno-exceptions`.
+
+Since *0.54.0* The `<lang>_thread_count` option can be used to control the
+value passed to `-s PTHREAD_POOL_SIZE` when using emcc. No other c/c++
+compiler supports this option.

docs/markdown/Reference-tables.md

@@ -37,10 +37,11 @@ These are return values of the `get_linker_id` method in a compiler object.
 
 | Value      | Linker family                               |
 | -----      | ---------------                             |
-| ld.bfd     | The GNU linker                              | 
+| ld.bfd     | The GNU linker                              |
 | ld.gold    | The GNU gold linker                         |
 | ld.lld     | The LLVM linker, with the GNU interface     |
 | ld.solaris | Solaris and illumos                         |
+| ld.wasm    | emscripten's wasm-ld linker                 |
 | ld64       | Apple ld64                                  |
 | link       | MSVC linker                                 |
 | lld-link   | The LLVM linker, with the MSVC interface    |

docs/markdown/snippets/emscripten_threads.md

@@ -0,0 +1,6 @@
+## Emscripten (emcc) now supports threads
+
+In addition to properly setting the compile and linker arguments, a new meson
+builtin has been added to control the PTHREAD_POOL_SIZE option,
+`-D<lang>_thread_count`, which may be set to any integer value greater than 0.
+If it set to 0 then the PTHREAD_POOL_SIZE option will not be passed.

docs/markdown/snippets/wasm_ld.md

@@ -0,0 +1,5 @@
+## Property support emscripten's wasm-ld
+
+Before 0.54.0 we treated emscripten as both compiler and linker, which isn't
+really true. It does have a linker, called wasm-ld (meson's name is ld.wasm).
+This is a special version of clang's lld. This will now be detected properly.

mesonbuild/compilers/c.py

@@ -27,7 +27,7 @@ from .mixins.intel import IntelGnuLikeCompiler, IntelVisualStudioLikeCompiler
 from .mixins.clang import ClangCompiler
 from .mixins.elbrus import ElbrusCompiler
 from .mixins.pgi import PGICompiler
-from .mixins.islinker import BasicLinkerIsCompilerMixin, LinkerEnvVarsMixin
+from .mixins.islinker import LinkerEnvVarsMixin
 from .mixins.emscripten import EmscriptenMixin
 from .compilers import (
     gnu_winlibs,
@@ -139,7 +139,7 @@ class AppleClangCCompiler(ClangCCompiler):
     _C18_VERSION = '>=11.0.0'
 
 
-class EmscriptenCCompiler(LinkerEnvVarsMixin, EmscriptenMixin, BasicLinkerIsCompilerMixin, ClangCCompiler):
+class EmscriptenCCompiler(EmscriptenMixin, LinkerEnvVarsMixin, ClangCCompiler):
     def __init__(self, exelist, version, for_machine: MachineChoice,
                  is_cross: bool, info: 'MachineInfo', exe_wrapper=None, **kwargs):
         if not is_cross:

mesonbuild/compilers/cpp.py

@@ -36,7 +36,7 @@ from .mixins.intel import IntelGnuLikeCompiler, IntelVisualStudioLikeCompiler
 from .mixins.clang import ClangCompiler
 from .mixins.elbrus import ElbrusCompiler
 from .mixins.pgi import PGICompiler
-from .mixins.islinker import BasicLinkerIsCompilerMixin, LinkerEnvVarsMixin
+from .mixins.islinker import LinkerEnvVarsMixin
 from .mixins.emscripten import EmscriptenMixin
 
 if T.TYPE_CHECKING:
@@ -207,7 +207,7 @@ class AppleClangCPPCompiler(ClangCPPCompiler):
     pass
 
 
-class EmscriptenCPPCompiler(LinkerEnvVarsMixin, EmscriptenMixin, BasicLinkerIsCompilerMixin, ClangCPPCompiler):
+class EmscriptenCPPCompiler(EmscriptenMixin, LinkerEnvVarsMixin, ClangCPPCompiler):
     def __init__(self, exelist, version, for_machine: MachineChoice,
                  is_cross: bool, info: 'MachineInfo', exe_wrapper=None, **kwargs):
         if not is_cross:

mesonbuild/compilers/mixins/emscripten.py

@@ -17,20 +17,13 @@
 import os.path
 import typing as T
 
-from ...mesonlib import MesonException
+from ... import coredata
 
-class EmscriptenMixin:
-    def get_option_link_args(self, options):
-        return []
-
-    def get_soname_args(self, *args, **kwargs):
-        raise MesonException('Emscripten does not support shared libraries.')
+if T.TYPE_CHECKING:
+    from ..environment import Environment
 
-    def get_allow_undefined_link_args(self) -> T.List[str]:
-        return ['-s', 'ERROR_ON_UNDEFINED_SYMBOLS=0']
 
-    def get_linker_output_args(self, output: str) -> T.List[str]:
-        return ['-o', output]
+class EmscriptenMixin:
 
     def _get_compile_output(self, dirname, mode):
         # In pre-processor mode, the output is sent to stdout and discarded
@@ -44,3 +37,17 @@ class EmscriptenMixin:
         else:
             suffix = 'wasm'
         return os.path.join(dirname, 'output.' + suffix)
+
+    def thread_flags(self, env: 'Environment') -> T.List[str]:
+        return ['-s', 'USE_PTHREADS=1']
+
+    def get_options(self):
+        opts = super().get_options()
+        opts.update({
+            '{}_thread_count'.format(self.language): coredata.UserIntegerOption(
+                'Number of threads to use in web assembly, set to 0 to disable',
+                (0, None, 4),  # Default was picked at random
+            ),
+        })
+
+        return opts

mesonbuild/compilers/mixins/islinker.py

@@ -130,3 +130,12 @@ class BasicLinkerIsCompilerMixin:
 
     def get_buildtype_linker_args(self, buildtype: str) -> T.List[str]:
         return []
+
+    def get_link_debugfile_name(self, target: str) -> str:
+        return ''
+
+    def thread_flags(self, env: 'Environment') -> T.List[str]:
+        return []
+
+    def thread_link_flags(self, env: 'Environment') -> T.List[str]:
+        return []

mesonbuild/environment.py

@@ -58,6 +58,7 @@ from .linkers import (
     XilinkDynamicLinker,
     CudaLinker,
     VisualStudioLikeLinkerMixin,
+    WASMDynamicLinker,
 )
 from functools import lru_cache
 from .compilers import (
@@ -963,9 +964,18 @@ class Environment:
             if 'Emscripten' in out:
                 cls = EmscriptenCCompiler if lang == 'c' else EmscriptenCPPCompiler
                 self.coredata.add_lang_args(cls.language, cls, for_machine, self)
+                # emcc cannot be queried to get the version out of it (it
+                # ignores -Wl,--version and doesn't have an alternative).
+                # Further, wasm-id *is* lld and will return `LLD X.Y.Z` if you
+                # call `wasm-ld --version`, but a special version of lld that
+                # takes different options.
+                p, o, _ = Popen_safe(['wasm-ld', '--version'])
+                linker = WASMDynamicLinker(
+                    compiler, for_machine, cls.LINKER_PREFIX,
+                    [], version=search_version(o))
                 return cls(
                     ccache + compiler, version, for_machine, is_cross, info,
-                    exe_wrap, full_version=full_version)
+                    exe_wrap, linker=linker, full_version=full_version)
 
             if 'armclang' in out:
                 # The compiler version is not present in the first line of output,

mesonbuild/linkers.py

@@ -693,6 +693,35 @@ class LLVMDynamicLinker(GnuLikeDynamicLinkerMixin, PosixDynamicLinkerMixin, Dyna
         return []
 
 
+class WASMDynamicLinker(GnuLikeDynamicLinkerMixin, PosixDynamicLinkerMixin, DynamicLinker):
+
+    """Emscripten's wasm-ld."""
+
+    def __init__(self, *args, **kwargs):
+        super().__init__('ld.wasm', *args, **kwargs)
+
+    def thread_link_flags(self, env: 'Environment') -> T.List[str]:
+        args = ['-s', 'USE_PTHREADS=1']
+        count = env.coredata.compiler_options[self.for_machine]['{}_thread_count'.format(self.language)].value  # type: int
+        if count:
+            args.extend(['-s', 'PTHREAD_POOL_SIZE={}'.format(count)])
+        return args
+
+    def get_allow_undefined_args(self) -> T.List[str]:
+        return ['-s', 'ERROR_ON_UNDEFINED_SYMBOLS=0']
+
+    def no_undefined_args(self) -> T.List[str]:
+        return ['-s', 'ERROR_ON_UNDEFINED_SYMBOLS=1']
+
+    def get_soname_args(self, env: 'Environment', prefix: str, shlib_name: str,
+                        suffix: str, soversion: str, darwin_versions: T.Tuple[str, str],
+                        is_shared_module: bool) -> T.List[str]:
+        raise mesonlib.MesonException('{} does not support shared libraries.'.format(self.id))
+
+    def get_asneeded_args(self) -> T.List[str]:
+        return []
+
+
 class CcrxDynamicLinker(DynamicLinker):
 
     """Linker for Renesis CCrx compiler."""

test cases/wasm/1 basic/hello.c

@@ -0,0 +1,7 @@
+#include <stdio.h>
+
+int main() {
+  printf("Hello World\n");
+  return 0;
+}
+

test cases/wasm/1 basic/meson.build

@@ -1,3 +1,4 @@
-project('emcctest', 'cpp')
+project('emcctest', 'c', 'cpp')
 
+executable('hello-c', 'hello.c')
 executable('hello', 'hello.cpp')

test cases/wasm/2 threads/meson.build

@@ -0,0 +1,10 @@
+project(
+  'threads',
+  'c', 'cpp',
+  default_options : ['cpp_std=c++11'],
+)
+
+dep_threads = dependency('threads')
+
+executable('threads-c', 'threads.c', dependencies : dep_threads)
+executable('threads-c++', 'threads.cpp', dependencies : dep_threads)

test cases/wasm/2 threads/threads.c

@@ -0,0 +1,21 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <pthread.h>
+
+void inthread(void * args) {
+    sleep(1);
+    printf("In thread\n");
+}
+
+int main() {
+#ifdef __EMSCRIPTEN_PTHREADS__
+    pthread_t thread_id;
+    printf("Before Thread\n"); 
+    pthread_create(&thread_id, NULL, (void *)*inthread, NULL); 
+    pthread_join(thread_id, NULL); 
+    printf("After Thread\n");
+    return 0;
+#else
+# error "threads not enabled\n"
+#endif
+}

test cases/wasm/2 threads/threads.cpp

@@ -0,0 +1,13 @@
+#include <unistd.h>
+#include <iostream>
+#include <thread>
+
+int main(void) {
+    std::cout << "Before thread" << std::endl;
+    std::thread t([]() {
+        sleep(1);
+        std::cout << "In a thread." << std::endl;
+    });
+    t.join();
+    std::cout << "After thread" << std::endl;
+}