diff --git a/src/tools/miri/src/shims/unix/android/foreign_items.rs b/src/tools/miri/src/shims/unix/android/foreign_items.rs
index 2b290b68c78c..f00bfb0a2078 100644
--- a/src/tools/miri/src/shims/unix/android/foreign_items.rs
+++ b/src/tools/miri/src/shims/unix/android/foreign_items.rs
@@ -28,21 +28,25 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         match link_name.as_str() {
             // File related shims
             "stat" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [path, buf] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 let result = this.stat(path, buf)?;
                 this.write_scalar(result, dest)?;
             }
             "lstat" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [path, buf] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 let result = this.lstat(path, buf)?;
                 this.write_scalar(result, dest)?;
             }
             "readdir" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [dirp] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 let result = this.readdir64("dirent", dirp)?;
                 this.write_scalar(result, dest)?;
             }
             "pread64" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [fd, buf, count, offset] = this.check_shim_sig(
                     shim_sig!(extern "C" fn(i32, *mut _, usize, libc::off64_t) -> isize),
                     link_name,
@@ -56,6 +60,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.read(fd, buf, count, Some(offset), dest)?;
             }
             "pwrite64" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [fd, buf, n, offset] = this.check_shim_sig(
                     shim_sig!(extern "C" fn(i32, *const _, usize, libc::off64_t) -> isize),
                     link_name,
@@ -70,6 +75,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write(fd, buf, count, Some(offset), dest)?;
             }
             "lseek64" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [fd, offset, whence] = this.check_shim_sig(
                     shim_sig!(extern "C" fn(i32, libc::off64_t, i32) -> libc::off64_t),
                     link_name,
diff --git a/src/tools/miri/src/shims/unix/foreign_items.rs b/src/tools/miri/src/shims/unix/foreign_items.rs
index 8eacdc3583d4..04ec260eccd0 100644
--- a/src/tools/miri/src/shims/unix/foreign_items.rs
+++ b/src/tools/miri/src/shims/unix/foreign_items.rs
@@ -143,6 +143,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "getcwd" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [buf, size] = this.check_shim_sig(
                     shim_sig!(extern "C" fn(*mut _, usize) -> *mut _),
                     link_name,
@@ -153,6 +154,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_pointer(result, dest)?;
             }
             "chdir" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [path] = this.check_shim_sig(
                     shim_sig!(extern "C" fn(*const _) -> i32),
                     link_name,
@@ -209,6 +211,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write(fd, buf, count, None, dest)?;
             }
             "pread" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [fd, buf, count, offset] = this.check_shim_sig(
                     shim_sig!(extern "C" fn(i32, *mut _, usize, libc::off_t) -> isize),
                     link_name,
@@ -222,6 +225,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.read(fd, buf, count, Some(offset), dest)?;
             }
             "pwrite" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [fd, buf, n, offset] = this.check_shim_sig(
                     shim_sig!(extern "C" fn(i32, *const _, usize, libc::off_t) -> isize),
                     link_name,
@@ -299,6 +303,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "unlink" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [path] = this.check_shim_sig(
                     shim_sig!(extern "C" fn(*const _) -> i32),
                     link_name,
@@ -309,6 +314,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "symlink" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [target, linkpath] = this.check_shim_sig(
                     shim_sig!(extern "C" fn(*const _, *const _) -> i32),
                     link_name,
@@ -324,6 +330,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "rename" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [oldpath, newpath] = this.check_shim_sig(
                     shim_sig!(extern "C" fn(*const _, *const _) -> i32),
                     link_name,
@@ -334,6 +341,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "mkdir" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [path, mode] = this.check_shim_sig(
                     shim_sig!(extern "C" fn(*const _, libc::mode_t) -> i32),
                     link_name,
@@ -344,6 +352,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "rmdir" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [path] = this.check_shim_sig(
                     shim_sig!(extern "C" fn(*const _) -> i32),
                     link_name,
@@ -354,6 +363,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "opendir" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [name] = this.check_shim_sig(
                     shim_sig!(extern "C" fn(*const _) -> *mut _),
                     link_name,
@@ -364,6 +374,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "closedir" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [dirp] = this.check_shim_sig(
                     shim_sig!(extern "C" fn(*mut _) -> i32),
                     link_name,
@@ -374,6 +385,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "lseek" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [fd, offset, whence] = this.check_shim_sig(
                     shim_sig!(extern "C" fn(i32, libc::off_t, i32) -> libc::off_t),
                     link_name,
@@ -398,6 +410,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "fsync" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [fd] = this.check_shim_sig(
                     shim_sig!(extern "C" fn(i32) -> i32),
                     link_name,
@@ -408,6 +421,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "fdatasync" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [fd] = this.check_shim_sig(
                     shim_sig!(extern "C" fn(i32) -> i32),
                     link_name,
@@ -659,6 +673,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_null(dest)?;
             }
             "pthread_key_delete" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [key] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 let key = this.read_scalar(key)?.to_bits(key.layout.size)?;
                 this.machine.tls.delete_tls_key(key)?;
@@ -666,6 +681,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_null(dest)?;
             }
             "pthread_getspecific" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [key] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 let key = this.read_scalar(key)?.to_bits(key.layout.size)?;
                 let active_thread = this.active_thread();
@@ -673,6 +689,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(ptr, dest)?;
             }
             "pthread_setspecific" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [key, new_ptr] =
                     this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 let key = this.read_scalar(key)?.to_bits(key.layout.size)?;
@@ -833,6 +850,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(res, dest)?;
             }
             "sched_yield" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 this.sched_yield()?;
                 this.write_null(dest)?;
@@ -941,6 +959,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "pthread_atfork" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [prepare, parent, child] =
                     this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 this.read_pointer(prepare)?;
diff --git a/src/tools/miri/src/shims/unix/freebsd/foreign_items.rs b/src/tools/miri/src/shims/unix/freebsd/foreign_items.rs
index fb2d3f758420..b94ee27c46a0 100644
--- a/src/tools/miri/src/shims/unix/freebsd/foreign_items.rs
+++ b/src/tools/miri/src/shims/unix/freebsd/foreign_items.rs
@@ -139,11 +139,13 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             // For those, we both intercept `func` and `call@FBSD_1.0` symbols cases
             // since freebsd 12 the former form can be expected.
             "stat" | "stat@FBSD_1.0" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [path, buf] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 let result = this.stat(path, buf)?;
                 this.write_scalar(result, dest)?;
             }
             "lstat" | "lstat@FBSD_1.0" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [path, buf] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 let result = this.lstat(path, buf)?;
                 this.write_scalar(result, dest)?;
@@ -154,6 +156,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "readdir" | "readdir@FBSD_1.0" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [dirp] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 let result = this.readdir64("dirent", dirp)?;
                 this.write_scalar(result, dest)?;
diff --git a/src/tools/miri/src/shims/unix/linux/foreign_items.rs b/src/tools/miri/src/shims/unix/linux/foreign_items.rs
index a7cb2ed11b2b..426bc28ce887 100644
--- a/src/tools/miri/src/shims/unix/linux/foreign_items.rs
+++ b/src/tools/miri/src/shims/unix/linux/foreign_items.rs
@@ -45,6 +45,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "pread64" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [fd, buf, count, offset] = this.check_shim_sig(
                     shim_sig!(extern "C" fn(i32, *mut _, usize, libc::off64_t) -> isize),
                     link_name,
@@ -58,6 +59,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.read(fd, buf, count, Some(offset), dest)?;
             }
             "pwrite64" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [fd, buf, n, offset] = this.check_shim_sig(
                     shim_sig!(extern "C" fn(i32, *const _, usize, libc::off64_t) -> isize),
                     link_name,
@@ -72,6 +74,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write(fd, buf, count, Some(offset), dest)?;
             }
             "lseek64" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [fd, offset, whence] = this.check_shim_sig(
                     shim_sig!(extern "C" fn(i32, libc::off64_t, i32) -> libc::off64_t),
                     link_name,
@@ -111,6 +114,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "readdir64" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [dirp] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 let result = this.readdir64("dirent64", dirp)?;
                 this.write_scalar(result, dest)?;
@@ -122,6 +126,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "statx" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [dirfd, pathname, flags, mask, statxbuf] =
                     this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 let result = this.linux_statx(dirfd, pathname, flags, mask, statxbuf)?;
diff --git a/src/tools/miri/src/shims/unix/macos/foreign_items.rs b/src/tools/miri/src/shims/unix/macos/foreign_items.rs
index f798f64441b1..204934f4c41d 100644
--- a/src/tools/miri/src/shims/unix/macos/foreign_items.rs
+++ b/src/tools/miri/src/shims/unix/macos/foreign_items.rs
@@ -47,11 +47,13 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "stat" | "stat$INODE64" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [path, buf] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 let result = this.stat(path, buf)?;
                 this.write_scalar(result, dest)?;
             }
             "lstat" | "lstat$INODE64" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [path, buf] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 let result = this.lstat(path, buf)?;
                 this.write_scalar(result, dest)?;
@@ -62,11 +64,13 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "opendir$INODE64" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [name] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 let result = this.opendir(name)?;
                 this.write_scalar(result, dest)?;
             }
             "readdir_r" | "readdir_r$INODE64" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [dirp, entry, result] =
                     this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 let result = this.macos_readdir_r(dirp, entry, result)?;
@@ -87,6 +91,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
 
             // Environment related shims
             "_NSGetEnviron" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 let environ = this.machine.env_vars.unix().environ();
                 this.write_pointer(environ, dest)?;
@@ -111,6 +116,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             }
 
             "mach_timebase_info" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [info] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 let result = this.mach_timebase_info(info)?;
                 this.write_scalar(result, dest)?;
@@ -118,14 +124,17 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
 
             // Access to command-line arguments
             "_NSGetArgc" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 this.write_pointer(this.machine.argc.expect("machine must be initialized"), dest)?;
             }
             "_NSGetArgv" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 this.write_pointer(this.machine.argv.expect("machine must be initialized"), dest)?;
             }
             "_NSGetExecutablePath" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [buf, bufsize] =
                     this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 this.check_no_isolation("`_NSGetExecutablePath`")?;
@@ -168,12 +177,14 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
 
             // Querying system information
             "pthread_get_stackaddr_np" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [thread] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 this.read_target_usize(thread)?;
                 let stack_addr = Scalar::from_uint(this.machine.stack_addr, this.pointer_size());
                 this.write_scalar(stack_addr, dest)?;
             }
             "pthread_get_stacksize_np" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [thread] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 this.read_target_usize(thread)?;
                 let stack_size = Scalar::from_uint(this.machine.stack_size, this.pointer_size());
diff --git a/src/tools/miri/src/shims/unix/solarish/foreign_items.rs b/src/tools/miri/src/shims/unix/solarish/foreign_items.rs
index fa8c86b025a7..f3918fdccf12 100644
--- a/src/tools/miri/src/shims/unix/solarish/foreign_items.rs
+++ b/src/tools/miri/src/shims/unix/solarish/foreign_items.rs
@@ -91,16 +91,19 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
 
             // File related shims
             "stat" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [path, buf] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 let result = this.stat(path, buf)?;
                 this.write_scalar(result, dest)?;
             }
             "lstat" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [path, buf] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 let result = this.lstat(path, buf)?;
                 this.write_scalar(result, dest)?;
             }
             "readdir" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [dirp] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 let result = this.readdir64("dirent", dirp)?;
                 this.write_scalar(result, dest)?;
@@ -122,6 +125,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             }
 
             "stack_getbounds" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [stack] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 let stack = this.deref_pointer_as(stack, this.libc_ty_layout("stack_t"))?;
 
@@ -140,6 +144,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             }
 
             "pset_info" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [pset, tpe, cpus, list] =
                     this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 // We do not need to handle the current process cpu mask, available_parallelism
diff --git a/src/tools/miri/src/shims/windows/foreign_items.rs b/src/tools/miri/src/shims/windows/foreign_items.rs
index 1905fb22e26a..0bdf6bb78505 100644
--- a/src/tools/miri/src/shims/windows/foreign_items.rs
+++ b/src/tools/miri/src/shims/windows/foreign_items.rs
@@ -148,6 +148,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         match link_name.as_str() {
             // Environment related shims
             "GetEnvironmentVariableW" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [name, buf, size] = this.check_shim_sig(
                     shim_sig!(extern "system" fn(*const _, *mut _, u32) -> u32),
                     link_name,
@@ -158,6 +159,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "SetEnvironmentVariableW" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [name, value] = this.check_shim_sig(
                     shim_sig!(extern "system" fn(*const _, *const _) -> winapi::BOOL),
                     link_name,
@@ -168,6 +170,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "GetEnvironmentStringsW" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [] = this.check_shim_sig(
                     shim_sig!(extern "system" fn() -> *mut _),
                     link_name,
@@ -178,6 +181,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_pointer(result, dest)?;
             }
             "FreeEnvironmentStringsW" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [env_block] = this.check_shim_sig(
                     shim_sig!(extern "system" fn(*mut _) -> winapi::BOOL),
                     link_name,
@@ -188,6 +192,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "GetCurrentDirectoryW" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [size, buf] = this.check_shim_sig(
                     shim_sig!(extern "system" fn(u32, *mut _) -> u32),
                     link_name,
@@ -198,6 +203,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "SetCurrentDirectoryW" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [path] = this.check_shim_sig(
                     shim_sig!(extern "system" fn(*const _) -> winapi::BOOL),
                     link_name,
@@ -208,6 +214,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "GetUserProfileDirectoryW" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [token, buf, size] = this.check_shim_sig(
                     shim_sig!(extern "system" fn(winapi::HANDLE, *mut _, *mut _) -> winapi::BOOL),
                     link_name,
@@ -218,6 +225,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "GetCurrentProcessId" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [] = this.check_shim_sig(
                     shim_sig!(extern "system" fn() -> u32),
                     link_name,
@@ -314,6 +322,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 )?;
             }
             "GetFullPathNameW" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [filename, size, buffer, filepart] = this.check_shim_sig(
                     shim_sig!(extern "system" fn(*const _, u32, *mut _, *mut _) -> u32),
                     link_name,
@@ -445,6 +454,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
 
             // Allocation
             "HeapAlloc" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [handle, flags, size] = this.check_shim_sig(
                     shim_sig!(extern "system" fn(winapi::HANDLE, u32, usize) -> *mut _),
                     link_name,
@@ -472,6 +482,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_pointer(ptr, dest)?;
             }
             "HeapFree" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [handle, flags, ptr] = this.check_shim_sig(
                     shim_sig!(extern "system" fn(winapi::HANDLE, u32, *mut _) -> winapi::BOOL),
                     link_name,
@@ -489,6 +500,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(Scalar::from_i32(1), dest)?;
             }
             "HeapReAlloc" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [handle, flags, old_ptr, size] = this.check_shim_sig(
                     shim_sig!(extern "system" fn(winapi::HANDLE, u32, *mut _, usize) -> *mut _),
                     link_name,
@@ -514,6 +526,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_pointer(new_ptr, dest)?;
             }
             "LocalFree" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [ptr] = this.check_shim_sig(
                     shim_sig!(extern "system" fn(winapi::HLOCAL) -> winapi::HLOCAL),
                     link_name,
@@ -577,6 +590,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
 
             // Querying system information
             "GetSystemInfo" => {
+                // FIXME: This does not have a direct test (#3179).
                 // Also called from `page_size` crate.
                 let [system_info] = this.check_shim_sig(
                     shim_sig!(extern "system" fn(*mut _) -> ()),
@@ -658,6 +672,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
 
             // Access to command-line arguments
             "GetCommandLineW" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [] = this.check_shim_sig(
                     shim_sig!(extern "system" fn() -> *mut _),
                     link_name,
@@ -672,6 +687,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
 
             // Time related shims
             "GetSystemTimeAsFileTime" | "GetSystemTimePreciseAsFileTime" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [filetime] = this.check_shim_sig(
                     shim_sig!(extern "system" fn(*mut _) -> ()),
                     link_name,
@@ -681,6 +697,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.GetSystemTimeAsFileTime(link_name.as_str(), filetime)?;
             }
             "QueryPerformanceCounter" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [performance_count] = this.check_shim_sig(
                     shim_sig!(extern "system" fn(*mut _) -> winapi::BOOL),
                     link_name,
@@ -691,6 +708,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "QueryPerformanceFrequency" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [frequency] = this.check_shim_sig(
                     shim_sig!(extern "system" fn(*mut _) -> winapi::BOOL),
                     link_name,
@@ -701,6 +719,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "Sleep" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [timeout] = this.check_shim_sig(
                     shim_sig!(extern "system" fn(u32) -> ()),
                     link_name,
@@ -711,6 +730,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.Sleep(timeout)?;
             }
             "CreateWaitableTimerExW" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [attributes, name, flags, access] = this.check_shim_sig(
                     shim_sig!(extern "system" fn(*mut _, *const _, u32, u32) -> winapi::HANDLE),
                     link_name,
@@ -748,6 +768,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(result, dest)?;
             }
             "WaitOnAddress" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [ptr_op, compare_op, size_op, timeout_op] = this.check_shim_sig(
                     // First pointer is volatile
                     shim_sig!(extern "system" fn(*mut _, *mut _, usize, u32) -> winapi::BOOL),
@@ -759,6 +780,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.WaitOnAddress(ptr_op, compare_op, size_op, timeout_op, dest)?;
             }
             "WakeByAddressSingle" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [ptr_op] = this.check_shim_sig(
                     shim_sig!(extern "system" fn(*mut _) -> ()),
                     link_name,
@@ -769,6 +791,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.WakeByAddressSingle(ptr_op)?;
             }
             "WakeByAddressAll" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [ptr_op] = this.check_shim_sig(
                     shim_sig!(extern "system" fn(*mut _) -> ()),
                     link_name,
@@ -781,6 +804,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
 
             // Dynamic symbol loading
             "GetProcAddress" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [module, proc_name] = this.check_shim_sig(
                     shim_sig!(extern "system" fn(winapi::HMODULE, *const _) -> winapi::FARPROC),
                     link_name,
@@ -936,6 +960,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
 
             // Miscellaneous
             "ExitProcess" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [code] = this.check_shim_sig(
                     shim_sig!(extern "system" fn(u32) -> ()),
                     link_name,
@@ -962,6 +987,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(Scalar::from_bool(true), dest)?;
             }
             "ProcessPrng" => {
+                // FIXME: This does not have a direct test (#3179).
                 // used by `std`
                 let [ptr, len] = this.check_shim_sig(
                     shim_sig!(extern "system" fn(*mut _, usize) -> winapi::BOOL),
@@ -1014,6 +1040,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_null(dest)?; // STATUS_SUCCESS
             }
             "GetConsoleScreenBufferInfo" => {
+                // FIXME: This does not have a direct test (#3179).
                 // `term` needs this, so we fake it.
                 let [console, buffer_info] = this.check_shim_sig(
                     shim_sig!(extern "system" fn(winapi::HANDLE, *mut _) -> winapi::BOOL),
@@ -1029,6 +1056,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_null(dest)?;
             }
             "GetStdHandle" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [which] = this.check_shim_sig(
                     shim_sig!(extern "system" fn(u32) -> winapi::HANDLE),
                     link_name,
@@ -1080,6 +1108,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(ret, dest)?;
             }
             "GetModuleFileNameW" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [handle, filename, size] = this.check_shim_sig(
                     shim_sig!(extern "system" fn(winapi::HMODULE, *mut _, u32) -> u32),
                     link_name,
@@ -1118,6 +1147,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 }
             }
             "FormatMessageW" => {
+                // FIXME: This does not have a direct test (#3179).
                 let [flags, module, message_id, language_id, buffer, size, arguments] = this
                     .check_shim_sig(
                         shim_sig!(
@@ -1159,6 +1189,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             }
 
             "_Unwind_RaiseException" => {
+                // FIXME: This does not have a direct test (#3179).
                 // This is not formally part of POSIX, but it is very wide-spread on POSIX systems.
                 // It was originally specified as part of the Itanium C++ ABI:
                 // https://itanium-cxx-abi.github.io/cxx-abi/abi-eh.html#base-throw.
diff --git a/src/tools/miri/tests/fail-dep/concurrency/windows_join_main.rs b/src/tools/miri/tests/fail-dep/concurrency/windows_join_main.rs
index da549a8d117d..a71778b1d0d4 100644
--- a/src/tools/miri/tests/fail-dep/concurrency/windows_join_main.rs
+++ b/src/tools/miri/tests/fail-dep/concurrency/windows_join_main.rs
@@ -12,7 +12,7 @@ use windows_sys::Win32::System::Threading::{INFINITE, WaitForSingleObject};
 
 // XXX HACK: This is how miri represents the handle for thread 0.
 // This value can be "legitimately" obtained by using `GetCurrentThread` with `DuplicateHandle`
-// but miri does not implement `DuplicateHandle` yet.
+// but miri does not implement `DuplicateHandle` yet. (FIXME: it does now.)
 const MAIN_THREAD: HANDLE = (2i32 << 29) as HANDLE;
 
 fn main() {