[Bug binutils/11977] New: ld updates output timestamp even when compiler fails

[jklowden at schemamania dot org]

When provided with a spurious filename on the command line, ld updates the
output file's timestamp even if compilation fails.  Re-invoking make
consequently produces a message that the target is up to date.  

Consider two files: ldtest.h (empty, not included), and ldtest.C:

$ cat ldtest.C 
int
main( int argc, char *argv[] )
{
        return 0;
}

Build it, ruin the source, build it (fails), build it again (succeeds):

$ make ldtest.borked
c++ -o ldtest.borked ldtest.C ldtest.h
$ make break
<ldtest.C sed 's/return/r eturn/' > ldtest.c
mv ldtest.c ldtest.C
$ make ldtest.borked
c++ -o ldtest.borked ldtest.C ldtest.h
ldtest.C: In function ‘int main(int, char**)’:
ldtest.C:4: error: ‘r’ was not declared in this scope
ldtest.C:4: error: expected `;' before ‘eturn’
make: *** [ldtest.borked] Error 1
$ make ldtest.borked
make: `ldtest.borked' is up to date.

$ stat ldtest.C ldtest.borked | grep -E 'ldtest|Change'
  File: `ldtest.C'
Change: 2010-09-03 12:56:18.140130000 -0400
  File: `ldtest.borked'
Change: 2010-09-03 12:56:24.168658000 -0400

If ldtest.h is not on the command line, the binary is not updated:

$ make fix
<ldtest.C sed 's/r eturn/return/' > ldtest.c
mv ldtest.c ldtest.C
$ make ldtest
c++ -o ldtest ldtest.C
$ make break
<ldtest.C sed 's/return/r eturn/' > ldtest.c
mv ldtest.c ldtest.C
$ make ldtest
c++ -o ldtest ldtest.C
ldtest.C: In function ‘int main(int, char**)’:
ldtest.C:4: error: ‘r’ was not declared in this scope
ldtest.C:4: error: expected `;' before ‘eturn’
make: *** [ldtest] Error 1
$ make ldtest
c++ -o ldtest ldtest.C
ldtest.C: In function ‘int main(int, char**)’:
ldtest.C:4: error: ‘r’ was not declared in this scope
ldtest.C:4: error: expected `;' before ‘eturn’
make: *** [ldtest] Error 1

$ stat ldtest.C ldtest | grep -E 'ldtest|Change'
  File: `ldtest.C'
Change: 2010-09-03 13:05:18.469643000 -0400
  File: `ldtest'
Change: 2010-09-03 13:05:15.407893000 -0400

$ ld -V
GNU ld version 2.17.50.0.6-6.el5 20061020
  Supported emulations:
   elf_x86_64
   elf_i386
   i386linux

While one might argue GIGO, this is an easy mistake to make.  I submit ld should
make every effort not to produce invalid binaries, and in this case it discards
information from the compiler.

-- 
           Summary: ld updates output timestamp even when compiler fails
           Product: binutils
           Version: 2.17
            Status: NEW
          Severity: normal
          Priority: P2
         Component: binutils
        AssignedTo: unassigned at sources dot redhat dot com
        ReportedBy: jklowden at schemamania dot org
                CC: bug-binutils at gnu dot org
GCC target triplet: elf_x86_64


http://sourceware.org/bugzilla/show_bug.cgi?id=11977

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