[Bug driver/82236] New: Offloading with -fno-use-linker-plugin fails, poor diagnostics

[amonakov at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82236

            Bug ID: 82236
           Summary: Offloading with -fno-use-linker-plugin fails, poor
                    diagnostics
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Keywords: lto, openacc, openmp
          Severity: normal
          Priority: P3
         Component: driver
          Assignee: unassigned at gcc dot gnu.org
          Reporter: amonakov at gcc dot gnu.org
  Target Milestone: ---

When linker plugin is not used (either due to old Binutils, or
-fno-use-linker-plugin), compiling code with offloading fails:

int main()
{
#pragma omp target
  ;
}

$ gcc -Os -fopenmp -fno-use-linker-plugin
gcc: warning: ‘-x lto’ after last input file has no effect
gcc: fatal error: no input files
compilation terminated.
lto-wrapper: fatal error: ./gcc returned 1 exit status
compilation terminated.
collect2: fatal error: lto-wrapper returned 1 exit status
compilation terminated.

(even with -foffload=disable). Surprisingly, adding either -fno-lto or -flto
(huh?) suppresses the failure, but the offloading compiler is not invoked.

I think this used to "work" in simple situations and got completely broken by
fix for PR 68463. At least issuing a sensible diagnostic would be nice.