rust: Enable MinGW ABI

Part-of: <https://gitlab.freedesktop.org/gstreamer/cerbero/-/merge_requests/1583>

5 files changed, 58 insertions, 13 deletions

diff --git a/cerbero/bootstrap/rust.py b/cerbero/bootstrap/rust.py
index 58b5d365..dfe598cc 100644
--- a/cerbero/bootstrap/rust.py
+++ b/cerbero/bootstrap/rust.py
@@ -81,18 +81,21 @@ class RustBootstrapper(BootstrapperBase):
         self.build_triple = self.config.rust_build_triple
         self.target_triples = self.config.rust_target_triples
         if self.config.platform == Platform.WINDOWS:
-            # On Windows, build-tools always use MSVC so we need to always
-            # bootstrap $arch-windows-msvc
-            bs_triple = self.config.rust_triple(self.config.arch, self.config.platform, True)
-            if bs_triple not in self.target_triples:
-                self.target_triples.append(bs_triple)
+            tgt = set(self.target_triples)
+            # On Windows, build tools must be built using MSVC. However,
+            # the current variant determines the default target.
+            # So we need to always bootstrap $arch-windows-msvc,
+            # and override the build triple accordingly
+            self.build_triple = self.config.rust_triple(self.config.arch, self.config.platform, True)
+            tgt.add(self.build_triple)
             # rustup-init wants to always install both 64-bit and 32-bit
             # toolchains, so ensure that we fetch and install both
             archs = {Architecture.X86_64, Architecture.X86}
             other_arch = (archs - {self.config.arch}).pop()
-            arch_triple = self.config.rust_triple(other_arch, self.config.platform, self.config.variants.visualstudio)
-            if arch_triple not in self.target_triples:
-                self.target_triples.append(arch_triple)
+            # in both MSVC and MinGW ABIs
+            tgt.add(self.config.rust_triple(other_arch, self.config.platform, True))
+            tgt.add(self.config.rust_triple(other_arch, self.config.platform, False))
+            self.target_triples = list(tgt)
         self.fetch_urls = self.get_fetch_urls()
         self.fetch_urls_func = self.get_more_fetch_urls
         self.extract_steps = []
@@ -179,11 +182,15 @@ class RustBootstrapper(BootstrapperBase):
             entry = channel_data['pkg'][c]['target'][self.build_triple]
             urls += list(get_entry_urls(entry))
 
-        # And then maybe also rust-std for the target machine
+        # Then maybe also rust-std for the target machine
         for triple in self.target_triples:
             if triple != self.build_triple:
                 entry = channel_data['pkg']['rust-std']['target'][triple]
                 urls += list(get_entry_urls(entry))
+            # And rust-mingw for any MinGW targets
+            if 'windows-gnu' in triple:
+                entry = channel_data['pkg']['rust-mingw']['target'][triple]
+                urls += list(get_entry_urls(entry))
 
         return (urls, self.install_toolchain_for_cargoc_fetch)
 
diff --git a/cerbero/build/build.py b/cerbero/build/build.py
index 1c7dd742..8c0513db 100644
--- a/cerbero/build/build.py
+++ b/cerbero/build/build.py
@@ -1369,6 +1369,19 @@ class CargoC(Cargo):
     def __init__(self):
         Cargo.__init__(self)
 
+        # cargo-c ignores config.toml's rustflags, which are necessary for i386
+        # cross-build
+        self.target_triple = self.config.rust_triple(
+            self.config.target_arch, self.config.target_platform, self.using_msvc()
+        )
+        if self.target_triple == 'i686-pc-windows-gnu':
+            tgt = self.target_triple.upper().replace('-', '_')
+            self.set_env(f'CARGO_TARGET_{tgt}_LINKER', self.get_env('RUSTC_LINKER'))
+            link_args = []
+            for arg in shlex.split(self.get_env('RUSTC_LDFLAGS')):
+                link_args += ['-C', f'link-arg={arg}']
+            self.set_env('RUSTFLAGS', ' '.join(link_args))
+
     def get_cargoc_args(self):
         cargoc_args = [
             '--release',
diff --git a/config/windows.config b/config/windows.config
index f15d5f2c..ad68b146 100644
--- a/config/windows.config
+++ b/config/windows.config
@@ -6,9 +6,12 @@
 from cerbero.config import Architecture, Platform, Distro, FatalError
 from cerbero.utils import EnvValue, EnvValueArg, EnvValueCmd, EnvValuePath
 
-# Enable rust support by default only when building with MSVC
-# https://gitlab.freedesktop.org/gstreamer/cerbero/-/issues/381
-if not variants.mingw and not variants.uwp:
+# MinGW x86 requires changing GCC's exception model to DWARF2
+# See https://fedoraproject.org/wiki/Changes/Mingw32GccDwarf2
+mingw_incompatible_sjlj = variants.mingw and target_arch == Architecture.X86
+
+# Tracking bug: https://gitlab.freedesktop.org/gstreamer/cerbero/-/issues/381
+if not variants.uwp and not mingw_incompatible_sjlj:
     variants.override('rust', False)
 
 # We don't want anything from mingw or msys detected in configure and
@@ -146,6 +149,10 @@ msvc_env_for_build_system['CC'] = EnvValueCmd('cl')
 msvc_env_for_build_system['CXX'] = EnvValueCmd('cl')
 msvc_env_for_build_system['AR'] = EnvValueCmd('lib')
 
+# Rust
+mingw_env_for_toolchain['RUSTC_LDFLAGS'] = EnvValueArg(arch_flags + [f'-Wl,-m,i386pe'])
+mingw_env_for_toolchain['RUSTC_LINKER'] = cmd('gcc')
+
 # MinGW toolchain config env
 mingw_env_for_toolchain['LIBRARY_PATH'] = EnvValuePath([lib_dir])
 
diff --git a/recipes/gst-plugins-rs.recipe b/recipes/gst-plugins-rs.recipe
index 91f7f385..2ecc0150 100644
--- a/recipes/gst-plugins-rs.recipe
+++ b/recipes/gst-plugins-rs.recipe
@@ -5,6 +5,7 @@ from cerbero.utils import messages as m
 from cerbero.utils import shell, determine_num_cargo_jobs, determine_total_ram
 from pathlib import Path
 import re
+import shlex
 import shutil
 import tempfile
 
@@ -137,6 +138,17 @@ class Recipe(recipe.Recipe):
             self.cargo_features.append(f'gst{each}/v1_22')
         self.cargo_features.append('gst-plugin-webrtc/v1_22')
 
+        # The LIBRARY_PATH setting affects all invocations of GCC underneath
+        # Cargo, in particular those that link build scripts (that are meant to
+        # run on the host machine, not through wine).
+        # When creating these, a value for LIBRARY_PATH present will cause
+        # cross-mingw GCC to prefer libpthread.a for MinGW-w64 over the system
+        # libpthread, and hell breaks loose.
+        if self.config.target_platform == Platform.WINDOWS and \
+            self.config.platform != self.config.target_platform:
+            self.set_env('LDFLAGS')
+            self.set_env('LIBRARY_PATH')
+
     async def configure(self):
         # Check that the Cargo.toml version matches the recipe version
         toml_version = self.get_cargo_toml_version()
diff --git a/recipes/librsvg.recipe b/recipes/librsvg.recipe
index 7b450d63..6ac9cc11 100644
--- a/recipes/librsvg.recipe
+++ b/recipes/librsvg.recipe
@@ -70,6 +70,10 @@ class Recipe(recipe.Recipe):
             # Cargo tries to look up an import lib when LibraryType.BOTH
             # librsvg only generates the shared library
             self.library_type = LibraryType.SHARED
+            # GCC willfully obeys LIBRARY_PATH
+            if self.config.platform != self.config.target_platform:
+                self.set_env('LDFLAGS')
+                self.set_env('LIBRARY_PATH')
         self.target_triple = self.config.rust_triple(self.config.target_arch,
             self.config.target_platform, self.using_msvc())
         self.meson_options['triplet'] = self.target_triple
@@ -88,6 +92,7 @@ class Recipe(recipe.Recipe):
         s = '[build]\n' \
             f'target = "{self.target_triple}"\n'
         self.append_config_toml(s)
+
         if self.config.target_platform == Platform.ANDROID:
             # Use the compiler's forwarding
             # See https://android.googlesource.com/platform/ndk/+/master/docs/BuildSystemMaintainers.md#linkers
@@ -95,7 +100,7 @@ class Recipe(recipe.Recipe):
             link_args = []
             # We need to extract necessary linker flags from LDFLAGS which is
             # passed to the compiler
-            for arg in shlex.split(self.get_env('LDFLAGS', '')):
+            for arg in shlex.split(self.get_env('RUSTC_LDFLAGS', self.get_env('LDFLAGS'))):
                 link_args += ['-C', f"link-arg={arg}"]
             s = f'[target.{self.target_triple}]\n' \
                 f'linker = "{linker}"\n' \
@@ -111,6 +116,7 @@ class Recipe(recipe.Recipe):
             for p in path:
                 if msys2_prefix in p:
                     self.remove_env('PATH', p, sep=os.pathsep)
+
         await super().configure()
 
     async def compile(self):