Fix Moonshine Linux release link error on older glibc

crates/voxctrl-inference/Cargo.toml

@@ -22,6 +22,12 @@ whisper-rs = { version = "0.16" }
 [dev-dependencies]
 tempfile = { workspace = true }
 
+# Used by build.rs to compile the glibc __isoc23_* shim for the Moonshine
+# backend on Linux. `cc` is already in the build graph (whisper-rs-sys), so this
+# adds nothing to compile.
+[build-dependencies]
+cc = "1"
+
 [features]
 default = []
 cuda = ["whisper-rs/cuda"]

crates/voxctrl-inference/build.rs

@@ -0,0 +1,20 @@
+fn main() {
+    // The Moonshine backend statically links a prebuilt ONNX Runtime (via
+    // `ort` + `download-binaries`) that is built against glibc >= 2.38 and so
+    // references __isoc23_strtol/strtoll/... symbols. Linking that archive on an
+    // older-glibc host (our ubuntu-22.04 release runners ship glibc 2.35) fails
+    // with "undefined symbol". Compile and link a tiny shim that provides those
+    // symbols by forwarding to the classic libc functions, keeping the binary
+    // linkable and runnable on older glibc. Linux + `moonshine` feature only.
+    let moonshine = std::env::var_os("CARGO_FEATURE_MOONSHINE").is_some();
+    let linux = std::env::var("CARGO_CFG_TARGET_OS").as_deref() == Ok("linux");
+
+    println!("cargo:rerun-if-changed=src/isoc23_compat.c");
+    println!("cargo:rerun-if-changed=build.rs");
+
+    if moonshine && linux {
+        cc::Build::new()
+            .file("src/isoc23_compat.c")
+            .compile("voxctrl_isoc23_compat");
+    }
+}

crates/voxctrl-inference/src/isoc23_compat.c

@@ -0,0 +1,45 @@
+/*
+ * glibc __isoc23_* compatibility shims for the Moonshine backend.
+ *
+ * The prebuilt ONNX Runtime static library (pyke, pulled in by `ort` with
+ * `download-binaries`) is compiled against glibc >= 2.38. Under C23, glibc
+ * redirects strtol/strtoul/... to __isoc23_* symbols, so the static archive
+ * references e.g. __isoc23_strtol. Our release runners are ubuntu-22.04
+ * (glibc 2.35), which has no such symbols, and the static link fails with
+ * "undefined symbol: __isoc23_strtol".
+ *
+ * These forwarders provide the symbols by calling the classic libc functions,
+ * so the binary links and runs on older glibc while keeping the AppImage's low
+ * glibc floor. The only C23 difference is that base 0 also accepts a "0b"
+ * binary prefix; ONNX Runtime's integer config parsing does not depend on that,
+ * so forwarding to the classic functions is safe.
+ *
+ * Compiled and linked only for the `moonshine` feature on Linux (see build.rs).
+ */
+
+#include <stdlib.h>
+#include <inttypes.h>
+
+long __isoc23_strtol(const char *nptr, char **endptr, int base) {
+    return strtol(nptr, endptr, base);
+}
+
+long long __isoc23_strtoll(const char *nptr, char **endptr, int base) {
+    return strtoll(nptr, endptr, base);
+}
+
+unsigned long __isoc23_strtoul(const char *nptr, char **endptr, int base) {
+    return strtoul(nptr, endptr, base);
+}
+
+unsigned long long __isoc23_strtoull(const char *nptr, char **endptr, int base) {
+    return strtoull(nptr, endptr, base);
+}
+
+intmax_t __isoc23_strtoimax(const char *nptr, char **endptr, int base) {
+    return strtoimax(nptr, endptr, base);
+}
+
+uintmax_t __isoc23_strtoumax(const char *nptr, char **endptr, int base) {
+    return strtoumax(nptr, endptr, base);
+}