Msvc needs /O1 (which implies /Os) to generate smallest binaries

7 years ago · 4fc5c90853
1 changed files with 2 additions and 2 deletions
--- a/src/lib.rs
+++ b/src/lib.rs
@ -1054,8 +1054,8 @@ impl Build {
                cmd.args.push(crt_flag.into());

                match &opt_level[..] {
-                    "z" | "s" => cmd.args.push("/Os".into()),
-                    "1" => cmd.args.push("/O1".into()),
+                    // Msvc uses /O1 to enable all optimizations that minimize code size.
+                    "z" | "s" | "1" => cmd.args.push("/O1".into()),
                    // -O3 is a valid value for gcc and clang compilers, but not msvc. Cap to /O2.
                    "2" | "3" => cmd.args.push("/O2".into()),
                    _ => {}