On Fri, Jun 19, 2026 at 12:33:21PM +0200, Richard Biener wrote:
> On Thu, Jan 1, 2026 at 6:06 PM Lewis Hyatt <[email protected]> wrote:
> >
> > In the LTO testsuite, tests run by default with a variety of options. If
> > the dg-lto-options directive is used, the default list is replaced with just
> > the requested options, so there is no convenient way, for instance, to add a
> > given option like -Wall to all of the options being tested.
> >
> > This will be handy for testing `#pragma GCC diagnostic' in the next patch in
> > this series, so this patch adds a new directive dg-lto-additional-options
> > for that purpose. This keeps the list of options to test unchanged, and
> > just adds the requested options to all of them.
>
> Looks good to me, but the documentation should be in sourcebuild.texi
> as well.
>
Oh, thanks, I missed that. Below incremental patch adds some documentation
there, and I tried to clarify the existing documentation of dg-lto-options a
bit as well. Does that look OK please?
> What's the actual difference between dg-lto-additional-options and
> a dg-additional-options which we could just support for lto.exp? Is
> there any?
The current state of things is like this:
- A given LTO test consists of a main source file, and additional source
files to be compiled separately.
- dg-lto-options can be specified in the main file to change which
options are used for the test.
- The main options, specified either by the LTO_OPTIONS variable or by
dg-lto-options in the main file, are used for all source files in the
test.
- If a particular non-main source file needs to add other options, it
can use the plain dg-options directive to do that.
One potential source of confusion is that in most tests, dg-options
overwrites the default options, but for LTO, it appends to them. It probably
predates the dg-additional-options directive, but that might have been a
clearer name for it, since it behaves like dg-additional-options does here.
The fact that dg-lto-options overwrites the default options can be
inconvenient, because the default set is rather large, testing 6 different
variations that are also chosen dynamically according to whether the linker
plugin is available. So if you just want to, say, add -Wall to the test,
it's not practical to use dg-lto-options for that. You could add
{ dg-options "-Wall" } to append the option to all the non-main source files
in the test, but there is no way to do it for the main file. Only
dg-lto-options is supported there, and using it overwrites the default set
of options. So I thought dg-lto-additional-options could be useful,
especially since, for testing diagnostics, it is necessary to add some
options to all the compilations.
I think the name dg-lto-additional-options is consistent with
dg-lto-options, in that it is meant for options that apply to every source
file in the test. lto.exp does not currently allow dg-options or
dg-additional-options in the main file, but if it did, they would presumably
apply only to the main file, similar to how dg-options in a non-main file
applies only to that file.
-Lewis
-----<8-----
diff --git a/gcc/doc/sourcebuild.texi b/gcc/doc/sourcebuild.texi
index ef2ca9eab5e..fd5f88447fc 100644
--- a/gcc/doc/sourcebuild.texi
+++ b/gcc/doc/sourcebuild.texi
@@ -4108,8 +4108,17 @@ Unlike @code{dg-do}, @code{dg-lto-do} does not support
an optional
@item @{ dg-lto-options @{ @{ @var{options} @} [@{ @var{options} @}] @} [@{
target @var{selector} @}]@}
This directive provides a list of one or more sets of compiler options
-to override @var{LTO_OPTIONS}. Each test will be compiled and run with
-each of these sets of options.
+to override @var{LTO_OPTIONS}. Every test file will be compiled and
+run once for each of these sets of options. Individual source files
+within a test may also use @code{dg-options} to specify additional
+options to include.
+
+@item @{ dg-lto-additional-options @{ @{ @var{options} @} [@{ @var{options}
@}] @} [@{ target @var{selector} @}]@}
+This is similar to @code{dg-lto-options}, but rather than overriding
+@var{LTO_OPTIONS}, it appends the given options to each of the sets
+specified in @var{LTO_OPTIONS}. This can be used to add a given list
+of options to every compilation of all source files in the test,
+without otherwise changing which combinations of options are tested.
@item @{ dg-extra-ld-options @var{options} [@{ target @var{selector} @}]@}
This directive adds @var{options} to the linker options used.
