Add test case for 'link_syms' parameter.

Test to make sure using --defsym in the link_syms parameter causes
correct linker behavior between object files and static libraries for
both C and C++.

The C test validates that linking redirects from a symbol not defined
by the library to a symbol that is defined by the library.

The C++ test validates that linking redirects from one defined symbol
to another defined symbol.

Signed-off-by: Keith Packard <keithp@keithp.com>

test cases/common/281 link-syms/cpplib.cpp

@@ -0,0 +1,10 @@
+#define BUILDING_DLL
+#include "cpplib.h"
+
+int DLL_PUBLIC cppfunc(void) {
+    return 42;
+}
+
+int DLL_PUBLIC cppfunc_sym(void) {
+    return 43;
+}

test cases/common/281 link-syms/cpplib.h

@@ -0,0 +1,13 @@
+/* See http://gcc.gnu.org/wiki/Visibility#How_to_use_the_new_C.2B-.2B-_visibility_support */
+#if defined(_WIN32) || defined(__CYGWIN__)
+  #ifdef BUILDING_DLL
+    #define DLL_PUBLIC __declspec(dllexport)
+  #else
+    #define DLL_PUBLIC __declspec(dllimport)
+  #endif
+#else
+    #define DLL_PUBLIC __attribute__ ((visibility ("default")))
+#endif
+
+int DLL_PUBLIC cppfunc_sym(void);
+int DLL_PUBLIC cppfunc(void);

test cases/common/281 link-syms/cppmain.cpp

@@ -0,0 +1,5 @@
+#include "cpplib.h"
+
+int main(void) {
+    return cppfunc_sym() != 42;
+}

test cases/common/281 link-syms/libfile.c

@@ -0,0 +1,14 @@
+#if defined _WIN32 || defined __CYGWIN__
+  #define DLL_PUBLIC __declspec(dllexport)
+#else
+  #if defined __GNUC__
+    #define DLL_PUBLIC __attribute__ ((visibility("default")))
+  #else
+    #pragma message ("Compiler does not support symbol visibility.")
+    #define DLL_PUBLIC
+  #endif
+#endif
+
+int DLL_PUBLIC func(void) {
+    return 0;
+}

test cases/common/281 link-syms/main.c

@@ -0,0 +1,12 @@
+#if defined _WIN32 || defined __CYGWIN__
+  #define DLL_IMPORT __declspec(dllimport)
+#else
+  #define DLL_IMPORT
+#endif
+
+int DLL_IMPORT func_sym(void);
+int DLL_IMPORT func(void);
+
+int main(void) {
+    return func_sym();
+}

test cases/common/281 link-syms/meson.build

@@ -0,0 +1,29 @@
+project('link_syms linking test', ['c', 'cpp'])
+
+c_compiler = meson.get_compiler('c')
+
+has_link_defsym = c_compiler.has_link_argument('-Wl,--defsym=start=0')
+
+if has_link_defsym
+  c_link_syms = '-Wl,--defsym=func_sym=func'
+  cpp_link_syms = '-Wl,--defsym=_Z11cppfunc_symv=_Z7cppfuncv'
+else
+  message(c_compiler.get_linker_id() + ' does not support --defsym so skipping.')
+  c_link_syms = ''
+  cpp_link_syms = ''
+endif
+
+if c_link_syms != ''
+  lib = static_library('mylib', 'libfile.c', install : false)
+  exe = executable('prog', 'main.c',
+                   link_syms : c_link_syms,
+                   link_with : lib)
+
+  test('runtest', exe)
+
+  cpplib = static_library('mycpplib', 'cpplib.cpp')
+  cppexe = executable('cppprog', 'cppmain.cpp',
+                      link_syms : cpp_link_syms,
+                      link_with : cpplib)
+  test('cpptest', cppexe)
+endif

test cases/common/281 link-syms/test.json

@@ -0,0 +1,2 @@
+{
+}