Shorter and less error-prone rule for automatic prerequisite generation in the GNU Make manual

[Robert Jørgensgaard Engdahl]

Hello GNU Make bug-list subscribers

On

http://www.gnu.org/software/make/manual/make.html#Automatic-Prerequisites

The rule for automatically generating
prerequisites is

 %.d: %.c
           
 @set -e; rm -f $@; \
           
  $(CC) -M $(CPPFLAGS) $< > address@hidden; \
           
  sed 's,\($*\)\.o[ :]*,\1.o $@ : ,g' < address@hidden > $@; \
           
  rm -f address@hidden

but could be replaced with

%.d : %.c
        @$(CC)
-MT $@ -MT $*.o -MM $(CPPFLAGS)  $< > $@

This is simpler.
This fixes disagreements about object
file names between the sed command and the cc command, should the c file
not be found in the current directory.

Perhaps it would be time to make this
rule part of the default rules in GNU Make? In that case, the -MG option
should also be considered for avoiding errors when auto generated headers
are included, perhaps via an CCMFLAGS variable.

Best regards Robert

-------
Robert Jørgensgaard Engdahl
Cum Laude MSc. C.S. 
SW-Developer, R&D
Video Services & Applications

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