edg_prelink: prelinker does not resolve shared libraries passed with -l

[hakanrw]

Issue Summary

When eccp invokes the C++ prelinker for automatic template instantiation,
the prelinker resolves -lNAME only as libNAME.a. If a library is available
as libNAME.so but has no static archive, edg_prelink reports that the
library does not exist. The final linker invocation accepts the same -L and
-loptions.

Passing the shared library by its explicit path works, as does disabling
automatic instantiation.

Observed Behavior

Given a shared library with no corresponding static archive:

cc -fPIC -shared fixture.c -o libedg_prelink_fixture.so

the normal GCC driver accepts it:

c++ main.cc -L. -ledg_prelink_fixture -o gcc-example
LD_LIBRARY_PATH=. ./gcc-example

The equivalent eccp invocation fails during prelinking:

eccp main.cc -L. -ledg_prelink_fixture -o eccp-example

library "edg_prelink_fixture" does not exist in the specified library directories
C++ prelinker: error: command line error

Passing the same shared library by its explicit path succeeds while automatic
template instantiation remains enabled:

eccp main.cc ./libedg_prelink_fixture.so \
  -o eccp-explicit-example
LD_LIBRARY_PATH=. ./eccp-explicit-example

Disabling automatic instantiation with -tused --no_auto_instantiation also
avoids the failure because edg_prelink is not invoked.

Expected Behavior

edg_prelink should resolve -lNAME consistently with the linker selected by
the eccp toolchain configuration. In this example,
-L. -ledg_prelink_fixture should resolve libedg_prelink_fixture.so,
which would allow automatic template instantiation and the final link to
complete.

The lookup should not be hard-coded to lib<X>.so; it should also support
shared library filename patterns used on other platforms, such as .dylib
on macOS and .dll on Windows.

Additional Details

Reduced source used to create the shared library (fixture.c):

int fixture_answer(void)
{
  return 42;
}

Caller (main.cc):

extern "C" int fixture_answer(void);

int main()
{
  return fixture_answer() == 42 ? 0 : 1;
}

I acknowledge that:

• I have checked open issues and existing discussions before filing this report.