Auto merge of #3087 - kleisauke:getentropy-emscripten, r=JohnTitor

Add getentropy for Emscripten

Required by rust-lang/rust#107221.

~~Marked as draft because I could not find `libc-test/semver/emscripten.txt`, so it doesn't meet the checklist.~~ Fixed with commit 6a7bd43.

Author: bors

libc-test/build.rs

@@ -2566,7 +2566,8 @@ fn test_emscripten(target: &str) {
             // FIXME: The size has been changed when upgraded to musl 1.2.2
             "pthread_mutex_t" => true,
 
-            // FIXME: The size has been changed
+            // FIXME: Lowered from 16 to 8 bytes in
+            // llvm/llvm-project@d1a96e9
             "max_align_t" => true,
 
             // FIXME: The size has been changed due to time64
@@ -2579,20 +2580,13 @@ fn test_emscripten(target: &str) {
 
     cfg.skip_fn(move |name| {
         match name {
-            // FIXME: https://github.com/rust-lang/libc/issues/1272
-            "execv" | "execve" | "execvp" | "execvpe" | "fexecve" => true,
+            // Emscripten does not support fork/exec/wait or any kind of multi-process support
+            // https://github.com/emscripten-core/emscripten/blob/3.1.30/tools/system_libs.py#L973
+            "execv" | "execve" | "execvp" | "execvpe" | "fexecve" | "wait4" => true,
 
-            // FIXME: Investigate why CI is missing it.
+            // FIXME: Remove after emscripten-core/emscripten#18492 is released (> 3.1.30).
             "clearenv" => true,
 
-            // FIXME: Somehow the ctest cannot find it on emscripten:
-            //  = note: error: undefined symbol: wait4 (referenced by top-level compiled C/C++ code)
-            //  warning: Link with `-sLLD_REPORT_UNDEFINED` to get more information on undefined symbols
-            //  warning: To disable errors for undefined symbols use `-sERROR_ON_UNDEFINED_SYMBOLS=0`
-            //  warning: _wait4 may need to be added to EXPORTED_FUNCTIONS if it arrives from a system library
-            //  Error: Aborting compilation due to previous errors
-            "wait4" => true,
-
             _ => false,
         }
     });

libc-test/semver/TODO-unix.txt

@@ -1,5 +1,6 @@
-# These symbols are missing for the targets:
+# These symbols are no-op or missing on these targets:
 # * asmjs-unknown-emscripten
+# * wasm32-unknown-emscripten
 getpwuid_r
 pthread_atfork
 pthread_sigmask

libc-test/semver/emscripten.txt

@@ -0,0 +1 @@
+getentropy

src/unix/linux_like/emscripten/mod.rs

@@ -1724,7 +1724,7 @@ f! {
     pub fn major(dev: ::dev_t) -> ::c_uint {
         // see
         // https://github.com/emscripten-core/emscripten/blob/
-        // master/system/include/libc/sys/sysmacros.h
+        // main/system/lib/libc/musl/include/sys/sysmacros.h
         let mut major = 0;
         major |= (dev & 0x00000fff) >> 8;
         major |= (dev & 0xfffff000) >> 31 >> 1;
@@ -1734,7 +1734,7 @@ f! {
     pub fn minor(dev: ::dev_t) -> ::c_uint {
         // see
         // https://github.com/emscripten-core/emscripten/blob/
-        // master/system/include/libc/sys/sysmacros.h
+        // main/system/lib/libc/musl/include/sys/sysmacros.h
         let mut minor = 0;
         minor |= (dev & 0x000000ff) >> 0;
         minor |= (dev & 0xffffff00) >> 12;
@@ -1814,7 +1814,6 @@ extern "C" {
     ) -> ::c_int;
     pub fn getloadavg(loadavg: *mut ::c_double, nelem: ::c_int) -> ::c_int;
 
-    // Not available now on Android
     pub fn mkfifoat(dirfd: ::c_int, pathname: *const ::c_char, mode: ::mode_t) -> ::c_int;
     pub fn if_nameindex() -> *mut if_nameindex;
     pub fn if_freenameindex(ptr: *mut if_nameindex);
@@ -1882,6 +1881,8 @@ extern "C" {
         f: extern "C" fn(*mut ::c_void) -> *mut ::c_void,
         value: *mut ::c_void,
     ) -> ::c_int;
+
+    pub fn getentropy(buf: *mut ::c_void, buflen: ::size_t) -> ::c_int;
 }
 
 cfg_if! {