Reproducer:

"""
$ cat test.c
#include <inc1.h>
#include <inc2.h>
#include <inc3.h>
main()
{
}

$ cat inc1.h
#include <limits.h>

$ cat inc2.h
#include <string.h>

$ cat inc3.h
#include <stdio.h>

$ cpp -I. -nostdinc test.c
# 1 "test.c"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "testprogram.c"
# 1 "./inc1.h" 1
In file included from test.c:1:0:
./inc1.h:1:19: fatal error: limits.h: No such file or directory
 #include <limits.h>
                   ^
compilation terminated.
"""

  On rhel6 it did list all missing includes, that is, would print something
like:

"""
# 1 "test.c"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "test.c"
# 1 "./inc1.h" 1
In file included from test.c:1:0:
./inc1.h:1:19: error: limits.h: No such file or directory [enabled by default]
 #include <limits.h>
                   ^
# 2 "test.c" 2
# 1 "./inc2.h" 1
In file included from test.c:2:0:
./inc2.h:1:19: error: string.h: No such file or directory [enabled by default]
 #include <string.h>
                   ^
# 3 "test.c" 2
# 1 "./inc3.h" 1
In file included from test.c:3:0:
./inc3.h:1:18: error: stdio.h: No such file or directory [enabled by default]
 #include <stdio.h>
                  ^
# 4 "testprogram.c" 2

main()
{
}
"""

  It appears the previous behavior should happen if one also pass
-Wno-fatal-errors to cpp command line.

  Note that on rhel7 and newer it prints "fatal error: ...", and on rhel6
it prints "error: ...".

  A possible workaround is to run as:

$ ( export DEPENDENCIES_OUTPUT=1; export SUNPRO_DEPENDENCIES=1; cpp -I. -nostdinc test.c )

what will cause cpp related flags to be set to follow a code path where
it will not cause a fatal error, but print "warning: ..." and list all
missing include files.

  The current behavior is likely the expected, as when not including
a file, any new error/warning messages are likely bogus as it could be
interpreted very differently if the missing include was loaded. But user
relies on previous behavior.