Merge #2221

2221: Support using RTLD_NEXT r=kvark a=ZeGentzy

Signed-off-by: Hal Gentz <zegentzy@protonmail.com>

Depends on: ash-rs/ash#77 (comment)
PR checklist:
- [ ] `make` succeeds (on *nix)
- [ ] `make reftests` succeeds
- [x] tested examples with the following backends: vulkan on archlinux


Co-authored-by: Hal Gentz <zegentzy@protonmail.com>

Author: bors[bot]

src/backend/vulkan/Cargo.toml

@@ -13,6 +13,7 @@ workspace = "../../.."
 
 [features]
 default = ["winit"]
+use-rtld-next = ["shared_library"]
 
 [lib]
 name = "gfx_backend_vulkan"
@@ -21,8 +22,8 @@ name = "gfx_backend_vulkan"
 byteorder = "1"
 log = { version = "0.4", features = ["release_max_level_error"] }
 lazy_static = "1"
-shared_library = "0.1"
-ash = "0.24.3"
+shared_library = { version = "0.1.9", optional = true }
+ash = "0.24.4"
 gfx-hal = { path = "../../hal", version = "0.1" }
 smallvec = "0.6"
 winit = { version = "0.16", optional = true }

src/backend/vulkan/src/lib.rs

@@ -7,6 +7,8 @@ extern crate gfx_hal as hal;
 #[macro_use]
 extern crate lazy_static;
 extern crate smallvec;
+#[cfg(feature = "use-rtld-next")]
+extern crate shared_library;
 
 #[cfg(windows)]
 extern crate winapi;
@@ -20,6 +22,7 @@ extern crate xcb;
 #[cfg(feature = "glsl-to-spirv")]
 extern crate glsl_to_spirv;
 
+#[cfg(not(feature = "use-rtld-next"))]
 use ash::{Entry, LoadingError};
 use ash::extensions as ext;
 use ash::version::{EntryV1_0, DeviceV1_0, InstanceV1_0, V1_0};
@@ -34,6 +37,11 @@ use std::borrow::Borrow;
 use std::ffi::{CStr, CString};
 use std::sync::Arc;
 
+#[cfg(feature = "use-rtld-next")]
+use shared_library::dynamic_library::{DynamicLibrary, SpecialHandles};
+#[cfg(feature = "use-rtld-next")]
+use ash::{EntryCustom, LoadingError};
+
 mod command;
 mod conv;
 mod device;
@@ -66,11 +74,25 @@ const SURFACE_EXTENSIONS: &'static [&'static str] = &[
     vk::VK_KHR_WIN32_SURFACE_EXTENSION_NAME,
 ];
 
+#[cfg(not(feature = "use-rtld-next"))]
 lazy_static! {
     // Entry function pointers
     pub static ref VK_ENTRY: Result<Entry<V1_0>, LoadingError> = Entry::new();
 }
 
+#[cfg(feature = "use-rtld-next")]
+lazy_static! {
+    // Entry function pointers
+    pub static ref VK_ENTRY: Result<EntryCustom<V1_0, ()>, LoadingError>
+        = EntryCustom::new_custom(
+            || Ok(()),
+            |_, name| unsafe {
+                DynamicLibrary::symbol_special(SpecialHandles::Next, &*name.to_string_lossy())
+                    .unwrap_or(ptr::null_mut())
+            }
+        );
+}
+
 pub struct RawInstance(pub ash::Instance<V1_0>, Option<(ext::DebugReport, vk::DebugReportCallbackEXT)>);
 impl Drop for RawInstance {
     fn drop(&mut self) {