From 90ed6b991b0cf11599ac6ede2e03d952368d588d Mon Sep 17 00:00:00 2001
From: William Wold <wm@wmww.sh>
Date: Sat, 12 Jan 2019 14:58:44 +0100
Subject: [PATCH 6/7] William enters the dlvsym fray

---
 src/common/sharedlibrary/CMakeLists.txt     | 27 +++++++++++++++++++++
 src/common/sharedlibrary/shared_library.cpp |  9 +++++++
 2 files changed, 36 insertions(+)

diff --git a/src/common/sharedlibrary/CMakeLists.txt b/src/common/sharedlibrary/CMakeLists.txt
index 0889ccc2f3..27436c5701 100644
--- a/src/common/sharedlibrary/CMakeLists.txt
+++ b/src/common/sharedlibrary/CMakeLists.txt
@@ -14,6 +14,33 @@
 #
 # Authored by: Alexandros Frantzis <alexandros.frantzis@canonical.com>
 
+include(CheckCXXSymbolExists)
+
+list(APPEND CMAKE_REQUIRED_LIBRARIES dl)
+list(APPEND CMAKE_REQUIRED_DEFINITIONS -D_GNU_SOURCE)
+
+check_cxx_symbol_exists("dlvsym" "dlfcn.h" HAS_DLVSYM)
+check_cxx_symbol_exists("dlsym" "dlfcn.h" HAS_DLSYM)
+
+if (NOT HAS_DLVSYM)
+  if (NOT HAS_DLSYM)
+    message(
+      FATAL_ERROR
+      "Could not detect dlvsym or dlsym"
+    )
+  endif()
+
+  set_source_files_properties (
+    "shared_library.cpp"
+    PROPERTIES COMPILE_DEFINITIONS MIR_DONT_USE_DLVSYM="1"
+  )
+
+  message(
+    WARNING
+    "dlvsym() not supported by libc. Mir may attempt to load ABI-incompatible platform modules"
+  )
+endif()
+
 add_library(mirsharedsharedlibrary OBJECT
   module_deleter.cpp
   shared_library.cpp
diff --git a/src/common/sharedlibrary/shared_library.cpp b/src/common/sharedlibrary/shared_library.cpp
index c97e26b040..80cbdb4186 100644
--- a/src/common/sharedlibrary/shared_library.cpp
+++ b/src/common/sharedlibrary/shared_library.cpp
@@ -17,6 +17,7 @@
  */
 
 #include "mir/shared_library.h"
+#include <mir/log.h>
 
 #include <boost/throw_exception.hpp>
 #include <boost/exception/info.hpp>
@@ -56,6 +57,13 @@ void* mir::SharedLibrary::load_symbol(char const* function_name) const
 
 void* mir::SharedLibrary::load_symbol(char const* function_name, char const* version) const
 {
+    // Some libc implementations (such as musl) do not support dlvsym
+
+#ifdef MIR_DONT_USE_DLVSYM
+    // Load the function without checking the version
+    log_debug("Cannot check \"%s\" symbol version is \"%s\": dlvsym() is unavailable", function_name, version);
+    return load_symbol(function_name);
+#else
     if (void* result = dlvsym(so, function_name, version))
     {
         return result;
@@ -64,4 +72,5 @@ void* mir::SharedLibrary::load_symbol(char const* function_name, char const* ver
     {
         BOOST_THROW_EXCEPTION(std::runtime_error(dlerror()));
     }
+#endif
 }
-- 
2.20.1