4 files changed, 9 insertions, 4 deletions
diff --git a/src/bootstrap/src/core/builder/mod.rs b/src/bootstrap/src/core/builder/mod.rs
index cc4fa953ddc..af3e3cc37b9 100644
--- a/src/bootstrap/src/core/builder/mod.rs
+++ b/src/bootstrap/src/core/builder/mod.rs
@@ -1388,7 +1388,7 @@ impl<'a> Builder<'a> {
         // Windows doesn't need dylib path munging because the dlls for the
         // compiler live next to the compiler and the system will find them
         // automatically.
-        if cfg!(windows) {
+        if cfg!(any(windows, target_os = "cygwin")) {
             return;
         }
 
diff --git a/src/bootstrap/src/utils/helpers.rs b/src/bootstrap/src/utils/helpers.rs
index b29c1fb3889..f2c3e8c0df4 100644
--- a/src/bootstrap/src/utils/helpers.rs
+++ b/src/bootstrap/src/utils/helpers.rs
@@ -130,7 +130,7 @@ pub fn is_debug_info(name: &str) -> bool {
 /// Returns the corresponding relative library directory that the compiler's
 /// dylibs will be found in.
 pub fn libdir(target: TargetSelection) -> &'static str {
-    if target.is_windows() { "bin" } else { "lib" }
+    if target.is_windows() || target.contains("cygwin") { "bin" } else { "lib" }
 }
 
 /// Adds a list of lookup paths to `cmd`'s dynamic library lookup path.
diff --git a/src/bootstrap/src/utils/shared_helpers.rs b/src/bootstrap/src/utils/shared_helpers.rs
index 1297a53d488..08e1c21e58e 100644
--- a/src/bootstrap/src/utils/shared_helpers.rs
+++ b/src/bootstrap/src/utils/shared_helpers.rs
@@ -20,7 +20,7 @@ use std::str::FromStr;
 /// Returns the environment variable which the dynamic library lookup path
 /// resides in for this platform.
 pub fn dylib_path_var() -> &'static str {
-    if cfg!(target_os = "windows") {
+    if cfg!(any(target_os = "windows", target_os = "cygwin")) {
         "PATH"
     } else if cfg!(target_vendor = "apple") {
         "DYLD_LIBRARY_PATH"
diff --git a/src/tools/miri/src/shims/native_lib.rs b/src/tools/miri/src/shims/native_lib.rs
index 0258a76c3e7..837e1b31cac 100644
--- a/src/tools/miri/src/shims/native_lib.rs
+++ b/src/tools/miri/src/shims/native_lib.rs
@@ -117,7 +117,12 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
         let mut info = std::mem::MaybeUninit::<libc::Dl_info>::uninit();
         unsafe {
             if libc::dladdr(*func.deref() as *const _, info.as_mut_ptr()) != 0 {
-                if std::ffi::CStr::from_ptr(info.assume_init().dli_fname).to_str().unwrap()
+                let info = info.assume_init();
+                #[cfg(target_os = "cygwin")]
+                let fname_ptr = info.dli_fname.as_ptr();
+                #[cfg(not(target_os = "cygwin"))]
+                let fname_ptr = info.dli_fname;
+                if std::ffi::CStr::from_ptr(fname_ptr).to_str().unwrap()
                     != _lib_path.to_str().unwrap()
                 {
                     return None;