From bb5f2ca3da821d7a8e865cd55a8d5d638e0aab22 Mon Sep 17 00:00:00 2001
From: Nirbheek Chauhan <nirbheek@centricular.com>
Date: Sun, 19 Aug 2018 22:05:48 +0530
Subject: find_library: Allow undefined symbols while linking

Shared libraries may not always be linkable without the use of other
libraries, so don't make it a linker error.
---
 mesonbuild/compilers/c.py       | 27 ++++++++++++++++++++++++++-
 mesonbuild/compilers/fortran.py |  3 +++
 2 files changed, 29 insertions(+), 1 deletion(-)

(limited to 'mesonbuild/compilers')

diff --git a/mesonbuild/compilers/c.py b/mesonbuild/compilers/c.py
index 0b169ca..3599a99 100644
--- a/mesonbuild/compilers/c.py
+++ b/mesonbuild/compilers/c.py
@@ -147,6 +147,30 @@ class CCompiler(Compiler):
         '''
         return self.get_no_optimization_args()
 
+    def get_allow_undefined_link_args(self):
+        '''
+        Get args for allowing undefined symbols when linking to a shared library
+        '''
+        if self.id == 'clang':
+            if self.clang_type == compilers.CLANG_OSX:
+                # Apple ld
+                return ['-Wl,-undefined,dynamic_lookup']
+            else:
+                # GNU ld and LLVM lld
+                return ['-Wl,--allow-shlib-undefined']
+        elif self.id == 'gcc':
+            if self.gcc_type == compilers.GCC_OSX:
+                # Apple ld
+                return ['-Wl,-undefined,dynamic_lookup']
+            else:
+                # GNU ld and LLVM lld
+                return ['-Wl,--allow-shlib-undefined']
+        elif self.id == 'msvc':
+            # link.exe
+            return ['/FORCE:UNRESOLVED']
+        # FIXME: implement other linkers
+        return []
+
     def get_output_args(self, target):
         return ['-o', target]
 
@@ -916,7 +940,8 @@ class CCompiler(Compiler):
         # Only try to find std libs if no extra dirs specified.
         if not extra_dirs or libname in self.internal_libs:
             args = ['-l' + libname]
-            if self.links(code, env, extra_args=args):
+            largs = self.linker_to_compiler_args(self.get_allow_undefined_link_args())
+            if self.links(code, env, extra_args=(args + largs)):
                 return args
             # Don't do a manual search for internal libs
             if libname in self.internal_libs:
diff --git a/mesonbuild/compilers/fortran.py b/mesonbuild/compilers/fortran.py
index c384f7f..1ee1fcb 100644
--- a/mesonbuild/compilers/fortran.py
+++ b/mesonbuild/compilers/fortran.py
@@ -144,6 +144,9 @@ end program prog
     def get_compiler_check_args(self):
         return CCompiler.get_compiler_check_args(self)
 
+    def get_allow_undefined_link_args(self):
+        return CCompiler.get_allow_undefined_link_args(self)
+
     def get_output_args(self, target):
         return CCompiler.get_output_args(self, target)
 
-- 
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