diff --git a/src/tools/miri/src/shims/foreign_items.rs b/src/tools/miri/src/shims/foreign_items.rs
index f6f91e58969..12f8facfd02 100644
--- a/src/tools/miri/src/shims/foreign_items.rs
+++ b/src/tools/miri/src/shims/foreign_items.rs
@@ -447,8 +447,7 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 } else {
                     // If this does not fit in an isize, return null and, on Unix, set errno.
                     if this.target_os_is_unix() {
-                        let einval = this.eval_libc("ENOMEM");
-                        this.set_last_error(einval)?;
+                        this.set_last_error(LibcError("ENOMEM"))?;
                     }
                     this.write_null(dest)?;
                 }
@@ -464,8 +463,7 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 } else {
                     // On size overflow, return null and, on Unix, set errno.
                     if this.target_os_is_unix() {
-                        let einval = this.eval_libc("ENOMEM");
-                        this.set_last_error(einval)?;
+                        this.set_last_error(LibcError("ENOMEM"))?;
                     }
                     this.write_null(dest)?;
                 }
@@ -486,8 +484,7 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 } else {
                     // If this does not fit in an isize, return null and, on Unix, set errno.
                     if this.target_os_is_unix() {
-                        let einval = this.eval_libc("ENOMEM");
-                        this.set_last_error(einval)?;
+                        this.set_last_error(LibcError("ENOMEM"))?;
                     }
                     this.write_null(dest)?;
                 }
diff --git a/src/tools/miri/src/shims/time.rs b/src/tools/miri/src/shims/time.rs
index 12c7679608d..6436823b0fd 100644
--- a/src/tools/miri/src/shims/time.rs
+++ b/src/tools/miri/src/shims/time.rs
@@ -81,9 +81,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         } else if relative_clocks.contains(&clk_id) {
             this.machine.clock.now().duration_since(this.machine.clock.epoch())
         } else {
-            let einval = this.eval_libc("EINVAL");
-            this.set_last_error(einval)?;
-            return interp_ok(Scalar::from_i32(-1));
+            return this.set_last_error_and_return_i32(LibcError("EINVAL"));
         };
 
         let tv_sec = duration.as_secs();
@@ -109,9 +107,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         // Using tz is obsolete and should always be null
         let tz = this.read_pointer(tz_op)?;
         if !this.ptr_is_null(tz)? {
-            let einval = this.eval_libc("EINVAL");
-            this.set_last_error(einval)?;
-            return interp_ok(Scalar::from_i32(-1));
+            return this.set_last_error_and_return_i32(LibcError("EINVAL"));
         }
 
         let duration = system_time_to_duration(&SystemTime::now())?;
@@ -323,9 +319,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         let duration = match this.read_timespec(&req)? {
             Some(duration) => duration,
             None => {
-                let einval = this.eval_libc("EINVAL");
-                this.set_last_error(einval)?;
-                return interp_ok(Scalar::from_i32(-1));
+                return this.set_last_error_and_return_i32(LibcError("EINVAL"));
             }
         };
 
diff --git a/src/tools/miri/src/shims/unix/foreign_items.rs b/src/tools/miri/src/shims/unix/foreign_items.rs
index 7ba98981920..355c93c444c 100644
--- a/src/tools/miri/src/shims/unix/foreign_items.rs
+++ b/src/tools/miri/src/shims/unix/foreign_items.rs
@@ -362,8 +362,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 // FreeBSD: https://man.freebsd.org/cgi/man.cgi?query=reallocarray
                 match this.compute_size_in_bytes(Size::from_bytes(size), nmemb) {
                     None => {
-                        let enmem = this.eval_libc("ENOMEM");
-                        this.set_last_error(enmem)?;
+                        this.set_last_error(LibcError("ENOMEM"))?;
                         this.write_null(dest)?;
                     }
                     Some(len) => {
@@ -653,13 +652,10 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 let chunk_size = CpuAffinityMask::chunk_size(this);
 
                 if this.ptr_is_null(mask)? {
-                    let efault = this.eval_libc("EFAULT");
-                    this.set_last_error(efault)?;
-                    this.write_int(-1, dest)?;
+                    this.set_last_error_and_return(LibcError("EFAULT"), dest)?;
                 } else if cpusetsize == 0 || cpusetsize.checked_rem(chunk_size).unwrap() != 0 {
                     // we only copy whole chunks of size_of::<c_ulong>()
-                    this.set_last_error(LibcError("EINVAL"))?;
-                    this.write_int(-1, dest)?;
+                    this.set_last_error_and_return(LibcError("EINVAL"), dest)?;
                 } else if let Some(cpuset) = this.machine.thread_cpu_affinity.get(&thread_id) {
                     let cpuset = cpuset.clone();
                     // we only copy whole chunks of size_of::<c_ulong>()
@@ -668,9 +664,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                     this.write_null(dest)?;
                 } else {
                     // The thread whose ID is pid could not be found
-                    let esrch = this.eval_libc("ESRCH");
-                    this.set_last_error(esrch)?;
-                    this.write_int(-1, dest)?;
+                    this.set_last_error_and_return(LibcError("ESRCH"), dest)?;
                 }
             }
             "sched_setaffinity" => {
@@ -695,9 +689,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 };
 
                 if this.ptr_is_null(mask)? {
-                    let efault = this.eval_libc("EFAULT");
-                    this.set_last_error(efault)?;
-                    this.write_int(-1, dest)?;
+                    this.set_last_error_and_return(LibcError("EFAULT"), dest)?;
                 } else {
                     // NOTE: cpusetsize might be smaller than `CpuAffinityMask::CPU_MASK_BYTES`.
                     // Any unspecified bytes are treated as zero here (none of the CPUs are configured).
@@ -713,8 +705,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                         }
                         None => {
                             // The intersection between the mask and the available CPUs was empty.
-                            this.set_last_error(LibcError("EINVAL"))?;
-                            this.write_int(-1, dest)?;
+                            this.set_last_error_and_return(LibcError("EINVAL"), dest)?;
                         }
                     }
                 }
@@ -770,9 +761,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 // macOS: https://keith.github.io/xcode-man-pages/getentropy.2.html
                 // Solaris/Illumos: https://illumos.org/man/3C/getentropy
                 if bufsize > 256 {
-                    let err = this.eval_libc("EIO");
-                    this.set_last_error(err)?;
-                    this.write_int(-1, dest)?;
+                    this.set_last_error_and_return(LibcError("EIO"), dest)?;
                 } else {
                     this.gen_random(buf, bufsize)?;
                     this.write_null(dest)?;
diff --git a/src/tools/miri/src/shims/unix/fs.rs b/src/tools/miri/src/shims/unix/fs.rs
index fcb824ab35b..8c502c578f6 100644
--- a/src/tools/miri/src/shims/unix/fs.rs
+++ b/src/tools/miri/src/shims/unix/fs.rs
@@ -787,13 +787,13 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             let ecode = if path.is_absolute() || dirfd == this.eval_libc_i32("AT_FDCWD") {
                 // since `path` is provided, either absolute or
                 // relative to CWD, `EACCES` is the most relevant.
-                this.eval_libc("EACCES")
+                LibcError("EACCES")
             } else {
                 // `dirfd` is set to target file, and `path` is empty
                 // (or we would have hit the `throw_unsup_format`
                 // above). `EACCES` would violate the spec.
                 assert!(empty_path_flag);
-                this.eval_libc("EBADF")
+                LibcError("EBADF")
             };
             return this.set_last_error_and_return_i32(ecode);
         }
@@ -1031,8 +1031,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         // Reject if isolation is enabled.
         if let IsolatedOp::Reject(reject_with) = this.machine.isolated_op {
             this.reject_in_isolation("`readdir`", reject_with)?;
-            let eacc = this.eval_libc("EBADF");
-            this.set_last_error(eacc)?;
+            this.set_last_error(LibcError("EBADF"))?;
             return interp_ok(Scalar::null_ptr(this));
         }
 
@@ -1449,11 +1448,11 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             if fd.is_tty(this.machine.communicate()) {
                 return interp_ok(Scalar::from_i32(1));
             } else {
-                this.eval_libc("ENOTTY")
+                LibcError("ENOTTY")
             }
         } else {
             // FD does not exist
-            this.eval_libc("EBADF")
+            LibcError("EBADF")
         };
         this.set_last_error(error)?;
         interp_ok(Scalar::from_i32(0))
@@ -1473,8 +1472,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         // Reject if isolation is enabled.
         if let IsolatedOp::Reject(reject_with) = this.machine.isolated_op {
             this.reject_in_isolation("`realpath`", reject_with)?;
-            let eacc = this.eval_libc("EACCES");
-            this.set_last_error(eacc)?;
+            this.set_last_error(LibcError("EACCES"))?;
             return interp_ok(Scalar::from_target_usize(0, this));
         }
 
@@ -1504,8 +1502,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                         // Note that we do not explicitly handle `FILENAME_MAX`
                         // (different from `PATH_MAX` above) as it is Linux-specific and
                         // seems like a bit of a mess anyway: <https://eklitzke.org/path-max-is-tricky>.
-                        let enametoolong = this.eval_libc("ENAMETOOLONG");
-                        this.set_last_error(enametoolong)?;
+                        this.set_last_error(LibcError("ENAMETOOLONG"))?;
                         return interp_ok(Scalar::from_target_usize(0, this));
                     }
                     processed_ptr
diff --git a/src/tools/miri/src/shims/unix/linux/mem.rs b/src/tools/miri/src/shims/unix/linux/mem.rs
index 4f2e17d50c8..d5f9669b360 100644
--- a/src/tools/miri/src/shims/unix/linux/mem.rs
+++ b/src/tools/miri/src/shims/unix/linux/mem.rs
@@ -24,7 +24,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         // old_address must be a multiple of the page size
         #[allow(clippy::arithmetic_side_effects)] // PAGE_SIZE is nonzero
         if old_address.addr().bytes() % this.machine.page_size != 0 || new_size == 0 {
-            this.set_last_error(this.eval_libc("EINVAL"))?;
+            this.set_last_error(LibcError("EINVAL"))?;
             return interp_ok(this.eval_libc("MAP_FAILED"));
         }
 
@@ -38,7 +38,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
 
         if flags & this.eval_libc_i32("MREMAP_MAYMOVE") == 0 {
             // We only support MREMAP_MAYMOVE, so not passing the flag is just a failure
-            this.set_last_error(this.eval_libc("EINVAL"))?;
+            this.set_last_error(LibcError("EINVAL"))?;
             return interp_ok(this.eval_libc("MAP_FAILED"));
         }
 
diff --git a/src/tools/miri/src/shims/unix/linux/sync.rs b/src/tools/miri/src/shims/unix/linux/sync.rs
index 941011bfac6..8640ce2e2cd 100644
--- a/src/tools/miri/src/shims/unix/linux/sync.rs
+++ b/src/tools/miri/src/shims/unix/linux/sync.rs
@@ -158,9 +158,7 @@ pub fn futex<'tcx>(
             } else {
                 // The futex value doesn't match the expected value, so we return failure
                 // right away without sleeping: -1 and errno set to EAGAIN.
-                let eagain = this.eval_libc("EAGAIN");
-                this.set_last_error(eagain)?;
-                this.write_scalar(Scalar::from_target_isize(-1, this), dest)?;
+                this.set_last_error_and_return(LibcError("EAGAIN"), dest)?;
             }
         }
         // FUTEX_WAKE: (int *addr, int op = FUTEX_WAKE, int val)
diff --git a/src/tools/miri/src/shims/unix/mem.rs b/src/tools/miri/src/shims/unix/mem.rs
index bf95cf27b83..9371edfc83d 100644
--- a/src/tools/miri/src/shims/unix/mem.rs
+++ b/src/tools/miri/src/shims/unix/mem.rs
@@ -57,11 +57,11 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
 
         // First, we do some basic argument validation as required by mmap
         if (flags & (map_private | map_shared)).count_ones() != 1 {
-            this.set_last_error(this.eval_libc("EINVAL"))?;
+            this.set_last_error(LibcError("EINVAL"))?;
             return interp_ok(this.eval_libc("MAP_FAILED"));
         }
         if length == 0 {
-            this.set_last_error(this.eval_libc("EINVAL"))?;
+            this.set_last_error(LibcError("EINVAL"))?;
             return interp_ok(this.eval_libc("MAP_FAILED"));
         }
 
@@ -103,11 +103,11 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
 
         let align = this.machine.page_align();
         let Some(map_length) = length.checked_next_multiple_of(this.machine.page_size) else {
-            this.set_last_error(this.eval_libc("EINVAL"))?;
+            this.set_last_error(LibcError("EINVAL"))?;
             return interp_ok(this.eval_libc("MAP_FAILED"));
         };
         if map_length > this.target_usize_max() {
-            this.set_last_error(this.eval_libc("EINVAL"))?;
+            this.set_last_error(LibcError("EINVAL"))?;
             return interp_ok(this.eval_libc("MAP_FAILED"));
         }
 
@@ -141,7 +141,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             return this.set_last_error_and_return_i32(LibcError("EINVAL"));
         };
         if length > this.target_usize_max() {
-            this.set_last_error(this.eval_libc("EINVAL"))?;
+            this.set_last_error(LibcError("EINVAL"))?;
             return interp_ok(this.eval_libc("MAP_FAILED"));
         }