[bug #21670] implicit rule ignored for prerequisite that is produced by .DEFAULT

[Guenter Egerer]

URL:
  <http://savannah.gnu.org/bugs/?21670>

                 Summary: implicit rule ignored for prerequisite that is
produced by .DEFAULT
                 Project: make
            Submitted by: egerer
            Submitted on: Thursday 11/29/2007 at 12:52
                Severity: 3 - Normal
              Item Group: Bug
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
       Component Version: 3.81
        Operating System: POSIX-Based
           Fixed Release: None

    _______________________________________________________

Details:

I've found a problem with GNU make 3.81 (built for i686-pc-linux-gnu).

The following makefile can be used to recreate the problem:

# -------------------------------------
CC = cc

.SUFFIXES:
.SUFFIXES: .c .o
.c.o:
        $(CC) -c $<

.DEFAULT:
        @if [ -f backup/$< ]; then \
          ln -s backup/$< . ;\
          echo "ln -s backup/$< .";\
        else  \
          echo "'$<' does not exist.";\
          false;\
        fi

prog:   hello.c hello.o
        $(CC) -o $@ hello.o
# -------------------------------------

The directory that contains this makefile should also
contain a subdirectory named "backup". That subdirectory
should contain a simple C source file named "hello.c".

Running "make" should create the file "hello.o" from the
file "hello.c" that is produced (in the current directory)
by the commands specified for the special built-in target
".DEFAULT".

Creation of the file "hello.c" works fine, but "make"
fails to produce "hello.o".

Here are the commands to reproduce the problem:

$ ls
backup  makefile
$ ls backup
hello.c
$ cat backup/hello.c
#include <stdio.h>

int main(void)
{
  printf("hello, world\n");
  return 0;
}
$ make -r
ln -s backup/hello.c .
'hello.o' does not exist.
make: *** [hello.o] Error 1
$ ls
backup  hello.c  makefile
$ 

After this I've run "make" in the debug mode:

$ rm hello.c
$ make -rd | nl -ba
     1  GNU Make 3.81
     2  Copyright (C) 2006  Free Software Foundation, Inc.
     3  This is free software; see the source for copying conditions.
     4  There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
     5  PARTICULAR PURPOSE.
     6
     7  This program built for i686-pc-linux-gnu
     8  Reading makefiles...
     9  Reading makefile `makefile'...
    10  Updating makefiles....
    11   Considering target file `makefile'.
    12    Looking for an implicit rule for `makefile'.
    13    No implicit rule found for `makefile'.
    14    Using default commands for `makefile'.
    15    Finished prerequisites of target file `makefile'.
    16   No need to remake target `makefile'.
    17  Updating goal targets....
    18  Considering target file `prog'.
    19   File `prog' does not exist.
    20    Considering target file `hello.c'.
    21     File `hello.c' does not exist.
    22     Looking for an implicit rule for `hello.c'.
    23     No implicit rule found for `hello.c'.
    24     Using default commands for `hello.c'.
    25     Finished prerequisites of target file `hello.c'.
    26    Must remake target `hello.c'.
    27  Putting child 0x080774d8 (hello.c) PID 10332 on the chain.
    28  Live child 0x080774d8 (hello.c) PID 10332
    29  ln -s backup/hello.c .
    30  Reaping winning child 0x080774d8 PID 10332
    31  Removing child 0x080774d8 PID 10332 from chain.
    32    Successfully remade target file `hello.c'.
    33    Considering target file `hello.o'.
    34     File `hello.o' does not exist.
    35     Looking for an implicit rule for `hello.o'.
    36     Trying pattern rule with stem `hello'.
    37     Trying implicit prerequisite `hello.c'.
    38     Trying pattern rule with stem `hello'.
    39     Trying implicit prerequisite `hello.c'.
    40     Looking for a rule with intermediate file `hello.c'.
    41      Avoiding implicit rule recursion.
    42     No implicit rule found for `hello.o'.
    43     Using default commands for `hello.o'.
    44     Finished prerequisites of target file `hello.o'.
    45    Must remake target `hello.o'.
    46  Putting child 0x080777f0 (hello.o) PID 10335 on the chain.
    47  Live child 0x080777f0 (hello.o) PID 10335
    48  'hello.o' does not exist.
    49  Reaping losing child 0x080777f0 PID 10335
make: *** [hello.o] Error 1
    50  Removing child 0x080777f0 PID 10335 from chain.

When "make" looks for an implicit rule for "hello.o" (line 35-41)
it should recognize that the target `hello.o' could be build
from the implicit prerequisite `hello.c' by applying the command
specified for the double-suffix rule ".c.o:" (line 6 of makefile).

In my opinion, it is a bug that GNU make 3.81 finds no implicit
rule for "hello.o" (line 42).




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File Attachments:


-------------------------------------------------------
Date: Thursday 11/29/2007 at 12:52  Name: makefile  Size: 332B   By: egerer

<http://savannah.gnu.org/bugs/download.php?file_id=14507>
-------------------------------------------------------
Date: Thursday 11/29/2007 at 12:52  Name: hello.c  Size: 79B   By: egerer

<http://savannah.gnu.org/bugs/download.php?file_id=14508>

    _______________________________________________________

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