Auto merge of #111698 - Amanieu:force-static-lib, r=petrochenkov

Force all native libraries to be statically linked when linking a static binary

Previously, `#[link]` without an explicit `kind = "static"` would confuse the linker and end up producing a dynamically linked library because of the `-Bdynamic` flag. However this binary would not work correctly anyways since it was linked with startup code for a static binary.

This PR solves this by forcing all native libraries to be statically linked when the output is a static binary that cannot link to dynamic libraries anyways.

Fixes #108878
Fixes #102993

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -2097,7 +2097,14 @@ fn linker_with_args<'a>(
     cmd.add_as_needed();
 
     // Local native libraries of all kinds.
-    add_local_native_libraries(cmd, sess, archive_builder_builder, codegen_results, tmpdir);
+    add_local_native_libraries(
+        cmd,
+        sess,
+        archive_builder_builder,
+        codegen_results,
+        tmpdir,
+        link_output_kind,
+    );
 
     // Upstream rust crates and their non-dynamic native libraries.
     add_upstream_rust_crates(
@@ -2107,10 +2114,18 @@ fn linker_with_args<'a>(
         codegen_results,
         crate_type,
         tmpdir,
+        link_output_kind,
     );
 
     // Dynamic native libraries from upstream crates.
-    add_upstream_native_libraries(cmd, sess, archive_builder_builder, codegen_results, tmpdir);
+    add_upstream_native_libraries(
+        cmd,
+        sess,
+        archive_builder_builder,
+        codegen_results,
+        tmpdir,
+        link_output_kind,
+    );
 
     // Link with the import library generated for any raw-dylib functions.
     for (raw_dylib_name, raw_dylib_imports) in
@@ -2365,6 +2380,7 @@ fn add_native_libs_from_crate(
     cnum: CrateNum,
     link_static: bool,
     link_dynamic: bool,
+    link_output_kind: LinkOutputKind,
 ) {
     if !sess.opts.unstable_opts.link_native_libraries {
         // If `-Zlink-native-libraries=false` is set, then the assumption is that an
@@ -2444,8 +2460,16 @@ fn add_native_libs_from_crate(
                 }
             }
             NativeLibKind::Unspecified => {
-                if link_dynamic {
-                    cmd.link_dylib(name, verbatim, true);
+                // If we are generating a static binary, prefer static library when the
+                // link kind is unspecified.
+                if !link_output_kind.can_link_dylib() && !sess.target.crt_static_allows_dylibs {
+                    if link_static {
+                        cmd.link_staticlib(name, verbatim)
+                    }
+                } else {
+                    if link_dynamic {
+                        cmd.link_dylib(name, verbatim, true);
+                    }
                 }
             }
             NativeLibKind::Framework { as_needed } => {
@@ -2472,6 +2496,7 @@ fn add_local_native_libraries(
     archive_builder_builder: &dyn ArchiveBuilderBuilder,
     codegen_results: &CodegenResults,
     tmpdir: &Path,
+    link_output_kind: LinkOutputKind,
 ) {
     if sess.opts.unstable_opts.link_native_libraries {
         // User-supplied library search paths (-L on the command line). These are the same paths
@@ -2501,6 +2526,7 @@ fn add_local_native_libraries(
         LOCAL_CRATE,
         link_static,
         link_dynamic,
+        link_output_kind,
     );
 }
 
@@ -2511,6 +2537,7 @@ fn add_upstream_rust_crates<'a>(
     codegen_results: &CodegenResults,
     crate_type: CrateType,
     tmpdir: &Path,
+    link_output_kind: LinkOutputKind,
 ) {
     // All of the heavy lifting has previously been accomplished by the
     // dependency_format module of the compiler. This is just crawling the
@@ -2588,6 +2615,7 @@ fn add_upstream_rust_crates<'a>(
             cnum,
             link_static,
             link_dynamic,
+            link_output_kind,
         );
     }
 }
@@ -2598,6 +2626,7 @@ fn add_upstream_native_libraries(
     archive_builder_builder: &dyn ArchiveBuilderBuilder,
     codegen_results: &CodegenResults,
     tmpdir: &Path,
+    link_output_kind: LinkOutputKind,
 ) {
     let search_path = OnceCell::new();
     for &cnum in &codegen_results.crate_info.used_crates {
@@ -2626,6 +2655,7 @@ fn add_upstream_native_libraries(
             cnum,
             link_static,
             link_dynamic,
+            link_output_kind,
         );
     }
 }

compiler/rustc_target/src/spec/mod.rs

@@ -675,6 +675,17 @@ impl LinkOutputKind {
             _ => return None,
         })
     }
+
+    pub fn can_link_dylib(self) -> bool {
+        match self {
+            LinkOutputKind::StaticNoPicExe | LinkOutputKind::StaticPicExe => false,
+            LinkOutputKind::DynamicNoPicExe
+            | LinkOutputKind::DynamicPicExe
+            | LinkOutputKind::DynamicDylib
+            | LinkOutputKind::StaticDylib
+            | LinkOutputKind::WasiReactorExe => true,
+        }
+    }
 }
 
 impl fmt::Display for LinkOutputKind {

src/doc/rustc/src/command-line-arguments.md

@@ -58,8 +58,8 @@ Example: `-l static:+whole-archive=mylib`.
 
 The kind of library and the modifiers can also be specified in a [`#[link]`
 attribute][link-attribute]. If the kind is not specified in the `link`
-attribute or on the command-line, it will link a dynamic library if available,
-otherwise it will use a static library. If the kind is specified on the
+attribute or on the command-line, it will link a dynamic library by default,
+except when building a static executable. If the kind is specified on the
 command-line, it will override the kind specified in a `link` attribute.
 
 The name used in a `link` attribute may be overridden using the form `-l