[Bug preprocessor/70270] New: Spurious line directive with -g

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70270

            Bug ID: 70270
           Summary: Spurious line directive with -g
           Product: gcc
           Version: 5.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: preprocessor
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rguenth at gcc dot gnu.org
  Target Milestone: ---

When preprocessing with -g0 vs. -g I see

> ./xgcc -B. t.c -E | head -3
# 1 "t.c"
# 1 "<built-in>"
# 1 "<command-line>"

> ./xgcc -B. t.c -E -g | head -3
# 1 "t.c"
# 1 "/abuild/rguenther/trunk3-g/gcc//"
# 1 "<built-in>"

so a spurious directive

# 1 "/abuild/rguenther/trunk3-g/gcc//"

is added which may result in different line-map behavior of -save-temps
with -fcompare-debug vs. non-save-temps?