bindexplib: Always export executable symbols, even they are also readable

Previously bindexplib discarded read-only non-function symbols even in
executable/code sections, but in some specific cases they could still mark
functions.

An example is provided by nop.asm in the AuoExportDll test, which exports
a function only marked by a label. This symbol can be used from C/C++
code, but without this change it would result in an unresolved external
symbol when built as a DLL on Windows.

Source/bindexplib.cxx

@@ -308,7 +308,8 @@ public:
                   this->DataSymbols.insert(symbol);
                } else {
                   if ( pSymbolTable->Type  ||
-                       !(SectChar & IMAGE_SCN_MEM_READ)) {
+                       !(SectChar & IMAGE_SCN_MEM_READ) ||
+                       (SectChar & IMAGE_SCN_MEM_EXECUTE)) {
                      this->Symbols.insert(symbol);
                   } else {
                      // printf(" strange symbol: %s \n",symbol.c_str());

Tests/RunCMake/AutoExportDll/AutoExport.cmake

@@ -11,5 +11,11 @@ if(MSVC)
   set_target_properties(say PROPERTIES ENABLE_EXPORTS ON)
   add_library(autoexport_for_exec SHARED hello2.c)
   target_link_libraries(autoexport_for_exec say)
+  if(NOT MSVC_VERSION VERSION_LESS 1600)
+    enable_language(ASM_MASM)
+    target_sources(autoexport PRIVATE nop.asm)
+    set_property(SOURCE nop.asm PROPERTY COMPILE_FLAGS /safeseh)
+    target_compile_definitions(say PRIVATE HAS_JUSTNOP)
+  endif()
 endif()
 target_link_libraries(say autoexport autoexport2)

Tests/RunCMake/AutoExportDll/nop.asm

+IFDEF RAX
+ELSE
+.MODEL FLAT,C
+ENDIF
+
+SOME SEGMENT EXECUTE READ
+
+public justnop
+justnop:
+  ret
+
+END

Tests/RunCMake/AutoExportDll/say.cxx

@@ -12,6 +12,7 @@ int WINAPI foo();
 // test regular C
 int bar();
 int objlib();
+void justnop();
 }
 
 // test c++ functions
@@ -42,5 +43,8 @@ int main()
   bar();
   objlib();
   printf("\n");
+#ifdef HAS_JUSTNOP
+  justnop();
+#endif
   return 0;
 }