From: Shiz <hi@shiz.me>
From: Jakub Jirutka <jakub@jirutka.cz>
Date: Wed, 12 Apr 2017 23:28:09 +0200
Subject: [PATCH] Force rpath on prefer-dynamic

When you build a dynamic binary with `-C prefer-dynamic`, rustc links
dynamically even Rust libraries, built as shared objects. These are
installed in /usr/lib/rustlib/<TARGET>/lib/, the location that is not
on standard LD path, at least on Alpine.

Therefore such binary would be unusable when not built with `-C rpath`
(or manually specifying LD_LIBRARY_PATH). For that reason we implicitly
enable rpath when `prefer-dynamic` is enabled.

Also note that Rust normally installs identical copy of *.so files from
/usr/lib/rustlib/<TARGET>/lib/, where <TARGET> equals host triple, to
/usr/lib. That's why such fully dynamic binary may work on other
systems even without rpath or having rustlib on the LD path. However,
since these *.so libraries don't keep stable ABI, they should not be on
LD path, and thus we do not install them here (see
change-rpath-to-rustlib.patch).

--- a/src/librustc/session/config.rs
+++ b/src/librustc/session/config.rs
@@ -1368,6 +1368,11 @@
 
     let mut cg = build_codegen_options(matches, error_format);
 
+    // Force rpath addition on prefer-dynamic output.
+    if cg.prefer_dynamic {
+        cg.rpath = true;
+    }
+
     // Issue #30063: if user requests llvm-related output to one
     // particular path, disable codegen-units.
     if matches.opt_present("o") && cg.codegen_units != 1 {