dpkg-deb: Set correct default compression value for control.tar.gz member

Regression introduced in commit f1f9887b8f96965d6046857d12fda24c053c6d4b.

The compressor independent way to denote the default value has been to
use -1, but that needs to be fixed up to the actual default value per
compressor, before the compressor specific setup.

When using the gzip command-line tool this is a fatal error as it does
not recognize the argument «-c-1». When using the zlib shared library
this makes the code always default to the compression level 1, as ‘-’
is ignored by gzdopen().

The current minimal fix is to call compressor_check_params() when
setting up the default control.tar compressor paramaters, although
that makes the API hard to use correctly. This will be improved in
the future.

Closes: #786654

1 files changed, 2 insertions, 0 deletions

diff --git a/dpkg-deb/build.c b/dpkg-deb/build.c
index 3a68cad7e..94d75ff4f 100644
--- a/dpkg-deb/build.c
+++ b/dpkg-deb/build.c
@@ -527,6 +527,8 @@ do_build(const char *const *argv)
     control_compress_params.type = COMPRESSOR_TYPE_GZIP;
     control_compress_params.strategy = COMPRESSOR_STRATEGY_NONE;
     control_compress_params.level = -1;
+    if (!compressor_check_params(&control_compress_params, &err))
+      internerr("invalid control member compressor params: %s", err.str);
   }
 
   c2 = subproc_fork();