Fix the threadsafe-setenv example in the try_getenv case. (#158)

* Fix the threadsafe-setenv example in the `try_getenv` case.

* Install libglib2.0-dev in CI for qemu.

Author: sunfishcode

.github/workflows/main.yml

@@ -68,7 +68,7 @@ jobs:
       run: |
         set -ex
         sudo apt-get update
-        sudo apt-get install -y ${{ matrix.gcc_package }} ninja-build
+        sudo apt-get install -y ${{ matrix.gcc_package }} ninja-build libglib2.0-dev
         upcase=$(echo ${{ matrix.host_target }} | awk '{ print toupper($0) }' | sed 's/-/_/g')
         echo CARGO_TARGET_${upcase}_LINKER=${{ matrix.gcc }} >> $GITHUB_ENV
         echo CC_${{ matrix.target }}=${{ matrix.gcc }} >> $GITHUB_ENV

example-crates/threadsafe-setenv/src/main.rs

@@ -58,6 +58,6 @@ fn lookup_localhost() {
 fn do_getenv() {
     for _ in 0..1000 {
         let r = std::env::var("doesnotexist");
-        assert!(r.is_ok(), "env var should not exist");
+        assert!(!r.is_ok(), "env var should not exist");
     }
 }

tests/example_crates.rs

@@ -163,7 +163,21 @@ fn example_crate_dns() {
 }
 
 #[test]
-fn example_crate_threadsafe_setenv() {
+fn example_crate_threadsafe_setenv_getenv() {
+    test_crate(
+        "threadsafe-setenv",
+        &["try_getenv"],
+        &[],
+        "will call std::env::set_var() 100 times ...\n\
+         spawning thread to call std::env::var (will not crash: Rust holds lock for getenv)...\n\
+         exiting without error\n",
+        "",
+        None,
+    );
+}
+
+#[test]
+fn example_crate_threadsafe_setenv_lookup() {
     test_crate(
         "threadsafe-setenv",
         &[],