Auto merge of #95604 - nbdd0121:used2, r=petrochenkov

Generate synthetic object file to ensure all exported and used symbols participate in the linking

Fix #50007 and #47384

This is the synthetic object file approach that I described in https://github.com/rust-lang/rust/pull/95363#issuecomment-1079932354, allowing all exported and used symbols to be linked while still allowing them to be GCed.

Related #93791, #95363

r? `@petrochenkov`
cc `@carbotaniuman`

6 files changed, 43 insertions, 0 deletions

diff --git a/src/test/run-make-fulldeps/reproducible-build/linker.rs b/src/test/run-make-fulldeps/reproducible-build/linker.rs
index 998d1f32859..3dda6f190e4 100644
--- a/src/test/run-make-fulldeps/reproducible-build/linker.rs
+++ b/src/test/run-make-fulldeps/reproducible-build/linker.rs
@@ -25,6 +25,12 @@ fn main() {
         let mut contents = Vec::new();
         File::open(path).unwrap().read_to_end(&mut contents).unwrap();
 
+        // This file is produced during linking in a temporary directory.
+        let arg = if arg.ends_with("/symbols.o") || arg.ends_with("\\symbols.o") {
+            "symbols.o"
+        } else {
+            &*arg
+        };
         out.push_str(&format!("{}: {}\n", arg, hash(&contents)));
     }
 
diff --git a/src/test/run-make-fulldeps/symbol-visibility/Makefile b/src/test/run-make-fulldeps/symbol-visibility/Makefile
index dc55c947d89..4bb35f33ad3 100644
--- a/src/test/run-make-fulldeps/symbol-visibility/Makefile
+++ b/src/test/run-make-fulldeps/symbol-visibility/Makefile
@@ -54,9 +54,12 @@ all:
 	# Check that a Rust dylib does not export generics if -Zshare-generics=no
 	[ "$$($(NM) $(TMPDIR)/$(RDYLIB_NAME) | grep -v __imp_ | grep -c public_generic_function_from_rlib)" -eq "0" ]
 
+# FIXME(nbdd0121): This is broken in MinGW, see https://github.com/rust-lang/rust/pull/95604#issuecomment-1101564032
+ifndef IS_WINDOWS
 	# Check that an executable does not export any dynamic symbols
 	[ "$$($(NM) $(TMPDIR)/$(EXE_NAME) | grep -v __imp_ | grep -c public_c_function_from_rlib)" -eq "0" ]
 	[ "$$($(NM) $(TMPDIR)/$(EXE_NAME) | grep -v __imp_ | grep -c public_rust_function_from_exe)" -eq "0" ]
+endif
 
 
 	# Check the combined case, where we generate a cdylib and an rlib in the same
@@ -91,6 +94,8 @@ all:
 	[ "$$($(NM) $(TMPDIR)/$(RDYLIB_NAME) | grep -v __imp_ | grep -c public_rust_function_from_rlib)" -eq "1" ]
 	[ "$$($(NM) $(TMPDIR)/$(RDYLIB_NAME) | grep -v __imp_ | grep -c public_generic_function_from_rlib)" -eq "1" ]
 
+ifndef IS_WINDOWS
 	# Check that an executable does not export any dynamic symbols
 	[ "$$($(NM) $(TMPDIR)/$(EXE_NAME) | grep -v __imp_ | grep -c public_c_function_from_rlib)" -eq "0" ]
 	[ "$$($(NM) $(TMPDIR)/$(EXE_NAME) | grep -v __imp_ | grep -c public_rust_function_from_exe)" -eq "0" ]
+endif
diff --git a/src/test/run-make/issue-47384/Makefile b/src/test/run-make/issue-47384/Makefile
new file mode 100644
index 00000000000..f10365f8c88
--- /dev/null
+++ b/src/test/run-make/issue-47384/Makefile
@@ -0,0 +1,12 @@
+-include ../../run-make-fulldeps/tools.mk
+
+# only-linux
+# ignore-cross-compile
+
+all: main.rs
+	$(RUSTC) --crate-type lib lib.rs
+	$(RUSTC) --crate-type cdylib -Clink-args="-Tlinker.ld" main.rs
+	# Ensure `#[used]` and `KEEP`-ed section is there
+	objdump -s -j".static" $(TMPDIR)/libmain.so
+	# Ensure `#[no_mangle]` symbol is there
+	nm $(TMPDIR)/libmain.so | $(CGREP) bar
diff --git a/src/test/run-make/issue-47384/lib.rs b/src/test/run-make/issue-47384/lib.rs
new file mode 100644
index 00000000000..99508bcdaf3
--- /dev/null
+++ b/src/test/run-make/issue-47384/lib.rs
@@ -0,0 +1,12 @@
+mod foo {
+    #[link_section = ".rodata.STATIC"]
+    #[used]
+    static STATIC: [u32; 10] = [1; 10];
+}
+
+mod bar {
+    #[no_mangle]
+    extern "C" fn bar() -> i32 {
+        0
+    }
+}
diff --git a/src/test/run-make/issue-47384/linker.ld b/src/test/run-make/issue-47384/linker.ld
new file mode 100644
index 00000000000..2e70acab3f4
--- /dev/null
+++ b/src/test/run-make/issue-47384/linker.ld
@@ -0,0 +1,7 @@
+SECTIONS
+{
+    .static : ALIGN(4)
+    {
+        KEEP(*(.rodata.STATIC));
+    }
+}
diff --git a/src/test/run-make/issue-47384/main.rs b/src/test/run-make/issue-47384/main.rs
new file mode 100644
index 00000000000..02572632517
--- /dev/null
+++ b/src/test/run-make/issue-47384/main.rs
@@ -0,0 +1 @@
+extern crate lib;