[bug #59247] function shell eats a newline

[Paul D. Smith]

Update of bug #59247 (project make):

  Item Group:None => Enhancement


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[bug #59247] function shell eats a newline

[Paul D. Smith]

Follow-up Comment #3, bug #59247 (project make):

This behavior is not related to bug #59395; that issue has to do with how
target recipes are split into individual command lines.  This issue is
discussing how an individual command line (or in this case the arguments to
the shell function) are handled when they are sent to the shell (or not).

However, I am also not sure that the provided patch is correct.  This will
always convert a newline to a space, regardless, which may not be correct in
all situations (consider single-quoted strings for example).

I think there's a larger problem here.  Consider this makefile:


x := $(shell echo $(FOO))
all:;: x='$x'


The original request clearly expected that FOO would be treated the same way
as a shell variable.  In the shell you'd get this:


$ FOO='
foo
bar
'

$ echo $FOO
foo bar


But, it's not a shell variable it's a make variable!  Make variables are
expanded by make, before invoking the shell, and they don't follow the same
escaping and quoting rules as the shell does.  So, if we have the above
makefile and we run it like this:


$ make FOO='
foo
bar
'


then I'd expect that make would invoke the equivalent of this shell command:


/bin/sh -c 'echo 
foo
bar
'


and that would yield errors because the commands "foo" and "bar" cannot be
found.

Of course, if we had a makefile like this:


x := $(shell echo "$(FOO)")
all:;: x='$x'


(with quotes) then this would be the shell invocation:


/bin/sh -c 'echo "
foo
bar
"'


and the results (after newlines are converted on the output as discussed in
the manual) would be " foo bar"

So, I'm a bit unsure how to proceed here.  Clearly the current behavior is not
right, where adding a semicolon gives different output : the slow-path is
causing issues.  But I'm not sure that fixing it to work completely correctly
wouldn't be an issue with compatibility even though it's the right thing to
do.

The problem is the overly complex way that make invokes subshells in the "slow
path".  The slow path should be the SIMPLEST solution but instead it's more
complicated and I'm not sure why.  It's not documented anywhere how shell will
handle _input_ strings that contain newlines; it only talks about _output_
newlines, so I think that this behavior is more of an unanticipated result of
how the parsing is done than anything intended.  Which doesn't mean that it
won't be a backward-compatibility problem to change it.

I'll need to think about this a bit.

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[bug #59247] function shell eats a newline

[Jörg Schilling]

Follow-up Comment #2, bug #59247 (project make):

I am not sure whether your patch is the right fix.

Your bug may be related to bug 59395, I reported recently, but your patch does
not fix the problem in bug 59395.

In general, gmake has several oddities in the area of handling space, tab,
newline and backslash. I suspect that there may be a common reason that should
be investigated and fixed in one single shot



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[bug #59247] function shell eats a newline

[Dmitry Goncharov]

Follow-up Comment #1, bug #59247 (project make):

The patch in the attachment fixes the issue.

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[bug #59247] function shell eats a newline

[Dmitry Goncharov]

Additional Item Attachment, bug #59247 (project make):

File name: sv_59247_func_shell_eats_newline.diff Size:1 KB
   




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[bug #59247] function shell eats a newline

[Dmitry Goncharov]

URL:
  

 Summary: function shell eats a newline
 Project: make
Submitted by: dgoncharov
Submitted on: Sat 10 Oct 2020 06:24:33 PM UTC
Severity: 3 - Normal
  Item Group: None
  Status: None
 Privacy: Public
 Assigned to: None
 Open/Closed: Open
 Discussion Lock: Any
   Component Version: None
Operating System: None
   Fixed Release: None
   Triage Status: None

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Details:

A user reported a bug here

https://lists.gnu.org/archive/html/bug-make/2020-10/msg00016.html.

From:   Byrnes, Robert
Subject:embedded newlines in shell function variable expansion
Date:   Fri, 9 Oct 2020 15:03:24 +

If I use this Makefile ...


bash$ cat Makefile
FOO := $(shell echo $(ENTRIES) ; )
BAR := $(shell echo $(ENTRIES)   )

all:
@echo FOO = $(FOO)
@echo BAR = $(BAR)

.PHONY: all


... and set ENTRIES with embedded newlines, then this happens:


bash$ make 'ENTRIES=
blartz
blurfl
'
FOO = blartzblurfl
BAR = blartz blurfl





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