[Bug plugins/80514] New: --enable-plugin and config/gcc-plugin.m4

[dilyan.palauzov at aegee dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80514

            Bug ID: 80514
           Summary: --enable-plugin and config/gcc-plugin.m4
           Product: gcc
           Version: 6.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: plugins
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dilyan.palauzov at aegee dot org
  Target Milestone: ---

config/plugins.m4 is written in such a way, that the plugins are enabled,
whenever dlfcn.h or windows.h are found, even when --enable-plugins was not
specified.  So the default is to enable plugins, whenever possible, but to
disable plugins, even when --enable-plugins is enforced but the mentioned
headers are missing.

Under these circumstances ./configure --help shall print
  --disable-plugin  disable plugin support
to indicate that the user has to take only action, when she wants to disable
plugins.

config/gcc-plugin.m4 also tries to enable plugins by default, if
--enable-plugins was not explicitly provided.

The line "enable_plugin=$enableval," is not necessary, as this is the default
ACTION-IF-GIVEN, just put two consecutive commas to 

At https://gcc.gnu.org/install/configure.html the option --enable-plugin is not
mentioned.