Support linking to rust dylibs from a staticlib

compiler/rustc_metadata/src/dependency_format.rs

@@ -89,11 +89,12 @@ fn calculate_type(tcx: TyCtxt<'_>, ty: CrateType) -> DependencyList {
         // to try to eagerly statically link all dependencies. This is normally
         // done for end-product dylibs, not intermediate products.
         //
-        // Treat cdylibs similarly. If `-C prefer-dynamic` is set, the caller may
-        // be code-size conscious, but without it, it makes sense to statically
-        // link a cdylib.
-        CrateType::Dylib | CrateType::Cdylib if !sess.opts.cg.prefer_dynamic => Linkage::Static,
-        CrateType::Dylib | CrateType::Cdylib => Linkage::Dynamic,
+        // Treat cdylibs and staticlibs similarly. If `-C prefer-dynamic` is set,
+        // the caller may be code-size conscious, but without it, it makes sense
+        // to statically link a cdylib or staticlib.
+        CrateType::Dylib | CrateType::Cdylib | CrateType::Staticlib => {
+            if sess.opts.cg.prefer_dynamic { Linkage::Dynamic } else { Linkage::Static }
+        }
 
         // If the global prefer_dynamic switch is turned off, or the final
         // executable will be statically linked, prefer static crate linkage.
@@ -108,9 +109,6 @@ fn calculate_type(tcx: TyCtxt<'_>, ty: CrateType) -> DependencyList {
         // No linkage happens with rlibs, we just needed the metadata (which we
         // got long ago), so don't bother with anything.
         CrateType::Rlib => Linkage::NotLinked,
-
-        // staticlibs must have all static dependencies.
-        CrateType::Staticlib => Linkage::Static,
     };
 
     match preferred_linkage {
@@ -123,12 +121,11 @@ fn calculate_type(tcx: TyCtxt<'_>, ty: CrateType) -> DependencyList {
                 return v;
             }
 
-            // Staticlibs and static executables must have all static dependencies.
+            // Static executables must have all static dependencies.
             // If any are not found, generate some nice pretty errors.
-            if ty == CrateType::Staticlib
-                || (ty == CrateType::Executable
-                    && sess.crt_static(Some(ty))
-                    && !sess.target.crt_static_allows_dylibs)
+            if ty == CrateType::Executable
+                && sess.crt_static(Some(ty))
+                && !sess.target.crt_static_allows_dylibs
             {
                 for &cnum in tcx.crates(()).iter() {
                     if tcx.dep_kind(cnum).macros_only() {

tests/run-make/staticlib-dylib-linkage/Makefile

@@ -0,0 +1,27 @@
+include ../tools.mk
+
+TARGET_SYSROOT := $(shell $(RUSTC) --print sysroot)/lib/rustlib/$(TARGET)/lib
+
+ifdef IS_MSVC
+LIBSTD := $(wildcard $(TARGET_SYSROOT)/libstd-*.dll.lib)
+else
+LIBSTD := $(wildcard $(TARGET_SYSROOT)/$(call DYLIB_GLOB,std))
+STD := $(basename $(patsubst lib%,%, $(notdir $(LIBSTD))))
+endif
+
+all: $(call RUN_BINFILE,foo)
+	$(call RUN,foo)
+
+ifdef IS_MSVC
+CLIBS := $(TMPDIR)/foo.lib $(TMPDIR)/bar.dll.lib $(LIBSTD)
+$(call RUN_BINFILE,foo): $(call STATICLIB,foo)
+	$(CC) $(CFLAGS) foo.c $(CLIBS) $(call OUT_EXE,foo)
+else
+CLIBS := $(TMPDIR)/libfoo.a -lbar -l$(STD) -L $(TMPDIR) -L $(TARGET_SYSROOT)
+$(call RUN_BINFILE,foo): $(call STATICLIB,foo)
+	$(CC) $(CFLAGS) foo.c $(CLIBS) -o $(call RUN_BINFILE,foo)
+endif
+
+$(call STATICLIB,foo):
+	$(RUSTC) -C prefer-dynamic bar.rs
+	$(RUSTC) foo.rs

tests/run-make/staticlib-dylib-linkage/bar.rs

@@ -0,0 +1,5 @@
+#![crate_type = "dylib"]
+
+pub fn bar() {
+    println!("hello!");
+}

tests/run-make/staticlib-dylib-linkage/foo.c

@@ -0,0 +1,10 @@
+#include <assert.h>
+
+extern void foo();
+extern unsigned bar(unsigned a, unsigned b);
+
+int main() {
+  foo();
+  assert(bar(1, 2) == 3);
+  return 0;
+}

tests/run-make/staticlib-dylib-linkage/foo.rs

@@ -0,0 +1,13 @@
+#![crate_type = "staticlib"]
+
+extern crate bar;
+
+#[no_mangle]
+pub extern "C" fn foo() {
+    bar::bar();
+}
+
+#[no_mangle]
+pub extern "C" fn bar(a: u32, b: u32) -> u32 {
+    a + b
+}