Add no_wasm_shim feature

zstd-safe/zstd-sys/Cargo.toml

@@ -69,12 +69,13 @@ debug = [] # Enable zstd debug logs
 experimental = [] # Expose experimental ZSTD API
 legacy = [] # Enable legacy ZSTD support (for versions < zstd-0.8)
 non-cargo = [] # Silence cargo-specific build flags
-pkg-config = []
+pkg-config = [] # Use pkg-config to build the zstd C library.
 std = [] # Deprecated: we never use types from std.
 zstdmt = [] # Enable multi-thread support (with pthread)
 thin = [] # Optimize binary by size
 no_asm = [] # Disable ASM files (only on amd64 for decompression)
-zdict_builder = []
+zdict_builder = [] # Enable dictionary building (dictionary _using_ is always supported).
+no_wasm_shim = [] # Disable wasm shims (in case your wasm toolchain includes a C stdlib).
 
 # These two are for cross-language LTO.
 # Will only work if `clang` is used to build the C library.

zstd-safe/zstd-sys/build.rs

@@ -133,9 +133,10 @@ fn compile_zstd() {
     // Note that Emscripten already provides its own C standard library so
     // wasm32-unknown-emscripten should not be included here.
     // See: https://github.com/gyscos/zstd-rs/pull/209
-    let need_wasm_shim = env::var("TARGET").map_or(false, |target| {
-        target == "wasm32-unknown-unknown" || target == "wasm32-wasi"
-    });
+    let need_wasm_shim = !cfg!(feature = "no_wasm_shim")
+        && env::var("TARGET").map_or(false, |target| {
+            target == "wasm32-unknown-unknown" || target == "wasm32-wasi"
+        });
 
     if need_wasm_shim {
         cargo_print(&"rerun-if-changed=wasm-shim/stdlib.h");