From 581ea58b2a8378440fb445d18dc2d9193fe45bc6 Mon Sep 17 00:00:00 2001
From: Andy Polyakov <appro@cryptogams.org>
Date: Wed, 27 Sep 2023 15:56:32 +0200
Subject: [PATCH] Add test case for
 'cargo:rustc-link-arg=-defaultlib:oldnames'.

---
 cc-test/build.rs      | 15 ++++++++++++++-
 cc-test/src/NMakefile |  3 +--
 cc-test/src/msvcrt.c  |  3 +++
 cc-test/tests/all.rs  | 11 +++++++++++
 4 files changed, 29 insertions(+), 3 deletions(-)
 create mode 100644 cc-test/src/msvcrt.c

diff --git a/cc-test/build.rs b/cc-test/build.rs
index 695c75473..ddce80f1a 100644
--- a/cc-test/build.rs
+++ b/cc-test/build.rs
@@ -7,6 +7,12 @@ fn main() {
     fs::remove_dir_all(&out).unwrap();
     fs::create_dir(&out).unwrap();
 
+    let target = std::env::var("TARGET").unwrap();
+
+    if target.ends_with("msvc") {
+        env::set_var("CL", "-Zl"); // drop linker directives
+    }
+
     cc::Build::new()
         .file("src/foo.c")
         .flag_if_supported("-Wall")
@@ -21,7 +27,6 @@ fn main() {
         .include("src/include")
         .compile("bar");
 
-    let target = std::env::var("TARGET").unwrap();
     let file = target.split("-").next().unwrap();
     let file = format!(
         "src/{}.{}",
@@ -55,6 +60,14 @@ fn main() {
 
     if target.contains("windows") {
         cc::Build::new().file("src/windows.c").compile("windows");
+        if target.ends_with("msvc") && which::which("clang").is_ok() {
+            cc::Build::new()
+                .compiler("clang")
+                .define("_CRT_NONSTDC_NO_WARNINGS", None)
+                .file("src/msvcrt.c")
+                .compile("nonstdcrt");
+            println!("cargo:rustc-cfg=feature=\"msvcrt\"");
+        }
     }
 
     // Test that the `windows_registry` module will set PATH by looking for
diff --git a/cc-test/src/NMakefile b/cc-test/src/NMakefile
index 03c73dff0..6f27979f4 100644
--- a/cc-test/src/NMakefile
+++ b/cc-test/src/NMakefile
@@ -2,13 +2,12 @@ all: $(OUT_DIR)/msvc.lib $(OUT_DIR)/msvc.exe
 
 $(OUT_DIR)/msvc.lib: $(OUT_DIR)/msvc.o
 	lib -nologo -out:$(OUT_DIR)/msvc.lib $(OUT_DIR)/msvc.o
-	rc -h
 
 $(OUT_DIR)/msvc.o: src/msvc.c
 	$(CC) -nologo -c -Fo:$@ src/msvc.c -MD
 
 $(OUT_DIR)/msvc.exe: $(OUT_DIR)/msvc2.o
-	$(CC) -nologo -Fo:$@ $(OUT_DIR)/msvc2.o
+	$(CC) -nologo -Fo:$@ $(OUT_DIR)/msvc2.o /link msvcrt.lib
 
 $(OUT_DIR)/msvc2.o: src/msvc.c
 	$(CC) -nologo -c -Fo:$@ src/msvc.c -DMAIN -MD
diff --git a/cc-test/src/msvcrt.c b/cc-test/src/msvcrt.c
new file mode 100644
index 000000000..1784c4cca
--- /dev/null
+++ b/cc-test/src/msvcrt.c
@@ -0,0 +1,3 @@
+#include <stdlib.h>
+#include <string.h>
+void msvcrt() { free(strdup("")); }
diff --git a/cc-test/tests/all.rs b/cc-test/tests/all.rs
index a44730987..5f83aa5a5 100644
--- a/cc-test/tests/all.rs
+++ b/cc-test/tests/all.rs
@@ -50,6 +50,17 @@ fn msvc_here() {
     }
 }
 
+#[test]
+#[cfg(feature = "msvcrt")]
+fn msvcrt_here() {
+    extern "C" {
+        fn msvcrt();
+    }
+    unsafe {
+        msvcrt();
+    }
+}
+
 #[test]
 fn opt_linkage() {
     unsafe {