Bug 1670261 - Upgrade Glean, include glean-ffi and re-export its symb…

…ols. r=chutten

Differential Revision: https://phabricator.services.mozilla.com/D121084

Cargo.toml

@@ -105,4 +105,4 @@ path = "third_party/rust/mio"
 
 # Patch failure 0.1.8 to disable the backtrace feature by default. See bug 1608157.
 [patch.crates-io.failure]
-path = "third_party/rust/failure"
+path = "third_party/rust/failure"

toolkit/components/glean/Cargo.toml

@@ -6,7 +6,16 @@ edition = "2018"
 license = "MPL-2.0"
 
 [dependencies]
-glean = { version = "39.0.0", features = ["rkv-safe-mode"] }
+glean = { version = "40.0.0", features = ["rkv-safe-mode"] }
+# In theory we only need this for `target_os = "android"` builds.
+# Cargo has the ability to do that with `[target.'cfg(target_os = "android")'.dependencies]`.
+# However that seems to confuse `cbindgen` quite a lot;
+# it suddenly starts generating completely unrelated code and not adhering to the cbindgen.toml configuration
+# placed next to this file.
+# So for now we unconditionally depend on it, but in the code we only `extern crate` it on Android builds.
+# While `glean-ffi` is still built (I think it is),
+# it's not linked into the final library.
+glean-ffi = "40.0.0"
 log = "0.4"
 nserror = { path = "../../../xpcom/rust/nserror" }
 nsstring = { path = "../../../xpcom/rust/nsstring" }

toolkit/components/glean/api/Cargo.toml

@@ -8,7 +8,7 @@ publish = false
 [dependencies]
 bincode = "1.0"
 chrono = "0.4.10"
-glean = "39.0.0"
+glean = "40.0.0"
 inherent = "0.1.4"
 log = "0.4"
 nsstring = { path = "../../../../xpcom/rust/nsstring", optional = true }

toolkit/components/glean/src/lib.rs

@@ -30,6 +30,26 @@
 // compiled.
 pub extern crate fog;
 
+pub use glean_ffi;
+
+/// Workaround to force a re-export of the `no_mangle` symbols from `glean_ffi`
+///
+/// Due to how linking works and hides symbols the symbols from `glean_ffi` might not be
+/// re-exported and thus not usable.
+/// By forcing use of _at least one_ symbol in an exported function the functions will also be
+/// rexported.
+/// This is only required for debug builds (and `debug_assertions` is the closest thing we have to
+/// check that).
+/// In release builds we rely on LTO builds to take care of it.
+/// Our tests should ensure this actually happens.
+///
+/// See https://github.com/rust-lang/rust/issues/50007
+#[cfg(debug_assertions)]
+#[no_mangle]
+pub unsafe extern "C" fn _fog_force_reexport_donotcall() {
+    glean_ffi::glean_enable_logging();
+}
+
 #[macro_use]
 extern crate cstr;
 #[macro_use]