Auto merge of #41168 - Shizmob:jemalloc-musl, r=alexcrichton

Fix jemalloc support for musl

Just like DragonFlyBSD, using the same symbols as the system allocator will result in a segmentation fault at runtime due to allocator mismatches. As such, it's better to prefix the jemalloc symbols instead, avoiding crashes.

We encountered this problem on a dynamically-linked musl target (with patches to Rust to make that possible, see #40113). It may not show up immediately obviously on the current statically-linked CRT targets.

Author: bors

src/liballoc_jemalloc/build.rs

@@ -129,7 +129,7 @@ fn main() {
         // should be good to go!
         cmd.arg("--with-jemalloc-prefix=je_");
         cmd.arg("--disable-tls");
-    } else if target.contains("dragonfly") {
+    } else if target.contains("dragonfly") || target.contains("musl") {
         cmd.arg("--with-jemalloc-prefix=je_");
     }
 

src/liballoc_jemalloc/lib.rs

@@ -35,23 +35,23 @@ mod imp {
     // request it as unprefixing cause segfaults (mismatches in allocators).
     extern "C" {
         #[cfg_attr(any(target_os = "macos", target_os = "android", target_os = "ios",
-                       target_os = "dragonfly", target_os = "windows"),
+                       target_os = "dragonfly", target_os = "windows", target_env = "musl"),
                    link_name = "je_mallocx")]
         fn mallocx(size: size_t, flags: c_int) -> *mut c_void;
         #[cfg_attr(any(target_os = "macos", target_os = "android", target_os = "ios",
-                       target_os = "dragonfly", target_os = "windows"),
+                       target_os = "dragonfly", target_os = "windows", target_env = "musl"),
                    link_name = "je_rallocx")]
         fn rallocx(ptr: *mut c_void, size: size_t, flags: c_int) -> *mut c_void;
         #[cfg_attr(any(target_os = "macos", target_os = "android", target_os = "ios",
-                       target_os = "dragonfly", target_os = "windows"),
+                       target_os = "dragonfly", target_os = "windows", target_env = "musl"),
                    link_name = "je_xallocx")]
         fn xallocx(ptr: *mut c_void, size: size_t, extra: size_t, flags: c_int) -> size_t;
         #[cfg_attr(any(target_os = "macos", target_os = "android", target_os = "ios",
-                       target_os = "dragonfly", target_os = "windows"),
+                       target_os = "dragonfly", target_os = "windows", target_env = "musl"),
                    link_name = "je_sdallocx")]
         fn sdallocx(ptr: *mut c_void, size: size_t, flags: c_int);
         #[cfg_attr(any(target_os = "macos", target_os = "android", target_os = "ios",
-                       target_os = "dragonfly", target_os = "windows"),
+                       target_os = "dragonfly", target_os = "windows", target_env = "musl"),
                    link_name = "je_nallocx")]
         fn nallocx(size: size_t, flags: c_int) -> size_t;
     }