"Unrecognized preprocessor instruction" caused by "#" at start of lines in a multi-line quoted string in #system

[tueda]

It is unclear whether this is a bug or whether it is even supposed to work, but it might be fun to file this as an issue.

The following program prints 5 lines as expected:

#define flag

#ifdef `flag'
  #system echo "\
# 1
# 2
# 3
# 4
# 5"
#endif
.end

# 1
# 2
# 3
# 4
# 5

But if I comment out the line that defines flag, FORM reports 4 errors:

test.frm Line 7 ==> Unrecognized preprocessor instruction:
test.frm Line 8 ==> Unrecognized preprocessor instruction:
test.frm Line 9 ==> Unrecognized preprocessor instruction:
test.frm Line 10 ==> Unrecognized preprocessor instruction:

It seems that in this case FORM tries to parse # 1, # 2, ... as preprocessor instructions.