#20 -Werror -Wno-unused-parameter flagging error with NVHPC

[Carl Ponder]

These source-lines in lib/pfmlib_perf_event_pmu.c

    128 static perf_umask_t *perf_um, *perf_um_free, *perf_um_end;
    960                 perf_um_free = perf_um_end = NULL;

are triggering the error

"pfmlib_perf_event_pmu.c", line 128: error: variable "perf_um_end" was set but never used [set_but_not_used]
  static perf_umask_t *perf_um, *perf_um_free, *perf_um_end;

Evidently there are other lines in the file that reference the variable, so I'm not sure what' going on here.
This is the 4.14.1 release code, with the NVHPC 26.9 compiler.

[Carl Ponder]

The compile-line is

nvc -m64 -tp=native -fpic -noswitcherror -Masmkeyword -D__thread='' -mp -lpthread  -g -Wall -Werror -Wextra -Wno-unused-parameter -I. -I/usr/local/build/include -DCONFIG_PFMLIB_DEBUG -DCONFIG_PFMLIB_OS_LINUX -DCONFIG_PFMLIB_NOTRACEPOINT  -g -Wall -Werror -Wextra -Wno-unused-parameter -I. -I/usr/local/build/lib/../include -DCONFIG_PFMLIB_DEBUG -DCONFIG_PFMLIB_OS_LINUX -DCONFIG_PFMLIB_NOTRACEPOINT -DHAS_OPENAT -D_REENTRANT -I. -fvisibility=hidden -DCONFIG_PFMLIB_ARCH_ARM64 -I. -c pfmlib_common.c
nvc -m64 -tp=native -fpic -noswitcherror -Masmkeyword -D__thread='' -mp -lpthread  -g -Wall -Werror -Wextra -Wno-unused-parameter -I. -I/usr/local/build/include -DCONFIG_PFMLIB_DEBUG -DCONFIG_PFMLIB_OS_LINUX -DCONFIG_PFMLIB_NOTRACEPOINT  -g -Wall -Werror -Wextra -Wno-unused-parameter -I. -I/usr/local/build/lib/../include -DCONFIG_PFMLIB_DEBUG -DCONFIG_PFMLIB_OS_LINUX -DCONFIG_PFMLIB_NOTRACEPOINT -DHAS_OPENAT -D_REENTRANT -I. -fvisibility=hidden -DCONFIG_PFMLIB_ARCH_ARM64 -I. -c pfmlib_perf_event_pmu.c

I can suppress the failure by using the invocation-line

make DBG="-g -Wall -Wextra" ...

to remove the -Werror -Wno-unused-parameter flags. But I assume that the intent of the default is to flag this sort of coding issue.