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841faa3614
The cxx component re-injects its own archive late on the link line so its
stack-unwind wrappers take precedence over libgcc's (when C++ exceptions
are disabled). It does this through an INTERFACE helper, libgcc_cxx, that
carries `$<TARGET_FILE:${cxx}>`. That helper was linked back into the cxx
target with PUBLIC, which places it in the cxx archive's own
LINK_LIBRARIES, so the cxx target ends up transitively referencing its
own output file.
When CMake computes the cxx target's sources it walks the target's own
link implementation, encounters `$<TARGET_FILE:${cxx}>`, and to resolve the
file it needs the target's link language, which in turn needs its
sources. This loop makes generation fail with:
The SOURCES of "..." use a generator expression that depends on the
SOURCES themselves.
CMake only hits this when it reaches the cxx target standalone before the
target has been pulled into a link by a consumer, and whether that
happens depends on the project layout and target evaluation order. That
is why it surfaces only in some projects, while the examples build fine.
Link libgcc_cxx as INTERFACE instead of PUBLIC. A static archive is not
linked, so its private LINK_LIBRARIES are inert; consumers still receive
libgcc_cxx through INTERFACE_LINK_LIBRARIES, so the intended link order is
preserved. Removing the self-reference makes generation independent of
evaluation order.
Signed-off-by: Frantisek Hrbata <frantisek.hrbata@espressif.com>