newlib/espidf: Add espidf_picolibc cfg for picolibc O_* flag values

drinkcat · tgross35 · commit 434c916ceb68 · 2026-04-08T06:06:09.000Z
ESP-IDF v6.0 switched from newlib to picolibc as default C library.
Picolibc uses Linux-compatible O_APPEND/O_CREAT/O_TRUNC values which
differ from newlib. Add espidf_picolibc cfg to select the correct values.
diff --git a/build.rs b/build.rs
@@ -13,6 +13,8 @@ use std::{
 // make sure to add it to this list as well.
 const ALLOWED_CFGS: &[&str] = &[
     "emscripten_old_stat_abi",
+    // Should be enabled by users if esp-idf (>=6.0) is build with picolibc instead of newlib.
+    "espidf_picolibc",
     "espidf_time32",
     "freebsd10",
     "freebsd11",
diff --git a/src/unix/newlib/mod.rs b/src/unix/newlib/mod.rs
@@ -514,9 +514,17 @@ pub const F_DUPFD_CLOEXEC: c_int = 14;
 pub const O_RDONLY: c_int = 0;
 pub const O_WRONLY: c_int = 1;
 pub const O_RDWR: c_int = 2;
-pub const O_APPEND: c_int = 8;
-pub const O_CREAT: c_int = 512;
-pub const O_TRUNC: c_int = 1024;
+cfg_if! {
+    if #[cfg(espidf_picolibc)] {
+        pub const O_APPEND: c_int = 1024;
+        pub const O_CREAT: c_int = 64;
+        pub const O_TRUNC: c_int = 512;
+    } else {
+        pub const O_APPEND: c_int = 8;
+        pub const O_CREAT: c_int = 512;
+        pub const O_TRUNC: c_int = 1024;
+    }
+}
 pub const O_EXCL: c_int = 2048;
 pub const O_SYNC: c_int = 8192;
 pub const O_NONBLOCK: c_int = 16384;
