Try to ease the Rust compiler's pain

We apparently blew the stack on Emscripten during emulation so let's try to cut
down on the pain by running at most 1000 tests in one function, hopefully
reducing stack size

src/lib.rs

@@ -888,6 +888,7 @@ impl<'a> Generator<'a> {
 
         self.tests.push(format!("field_offset_size_{}", ty));
         t!(writeln!(self.rust, r#"
+            #[inline(never)]
             fn field_offset_size_{ty}() {{
         "#, ty = ty));
         for field in s.fields() {
@@ -973,6 +974,7 @@ impl<'a> Generator<'a> {
             uint64_t __test_align_{ty}(void) {{ return {align_of}({cty}); }}
         "#, ty = rust, cty = c, align_of = align_of));
         t!(writeln!(self.rust, r#"
+            #[inline(never)]
             fn size_align_{ty}() {{
                 extern {{
                     fn __test_size_{ty}() -> u64;
@@ -1003,6 +1005,7 @@ impl<'a> Generator<'a> {
             }}
         "#, ty = rust, cty = c));
         t!(writeln!(self.rust, r#"
+            #[inline(never)]
             fn sign_{ty}() {{
                 extern {{
                     fn __test_signed_{ty}() -> u32;
@@ -1049,6 +1052,7 @@ impl<'a> Generator<'a> {
 
         if rust_ty == "&str" {
             t!(writeln!(self.rust, r#"
+                #[inline(never)]
                 fn const_{name}() {{
                     extern {{
                         fn __test_const_{name}() -> *const *const u8;
@@ -1105,6 +1109,7 @@ impl<'a> Generator<'a> {
             }}
         "#, name = name, cname = cname, args = args, ret = cret, abi = abi));
         t!(writeln!(self.rust, r#"
+            #[inline(never)]
             fn fn_{name}() {{
                 extern {{
                     fn __test_fn_{name}() -> *mut u32;
@@ -1331,10 +1336,27 @@ impl<'a> Generator<'a> {
     }
 
     fn emit_run_all(&mut self) {
+        const N: usize = 1000;
+        let mut n = 0;
+        let mut tests = self.tests.clone();
+        while tests.len() > N {
+            let name = format!("run_group{}", n);
+            n += 1;
+            t!(writeln!(self.rust, "
+                #[inline(never)]
+                fn {}() {{
+            ", name));
+            for test in tests.drain(..1000) {
+                t!(writeln!(self.rust, "{}();", test));
+            }
+            t!(writeln!(self.rust, "}}"));
+            tests.push(name);
+        }
         t!(writeln!(self.rust, "
+            #[inline(never)]
             fn run_all() {{
         "));
-        for test in self.tests.iter() {
+        for test in tests.iter() {
             t!(writeln!(self.rust, "{}();", test));
         }
         t!(writeln!(self.rust, "