Bug ID: 84351
           Summary: Provide dependency information also when linking
           Product: gcc
           Version: 7.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
          Assignee: unassigned at gcc dot
          Reporter: jpakkane at gmail dot com
  Target Milestone: ---

The -M flag and its like is very useful for reliable dependencies. It would be
great if the same would work also when linking.

The use case is the following. Suppose you build a project with a dependency
that comes in via pkg-config. The eventual link line looks like this:

gcc -o final_exe source.o -L/path/to/my/place -L/path/to/somewhere/else -lmydep

It is very difficult to tell where the dependency library will be picked up
from. If the user updates any library by doing a "make/ninja install" from the
dependency file, then it is hard to know that the dependency libraries have
changed and thus require a rebuild. (usually doing an install updates headers,
which _do_ trigger a rebuild but some systems only overwrite installed files if
they have changed so looking only at header files is not reliable).

If linking supported generating dependency files like -M does for source
compilations, this would not be a problem and

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