From be818361b9a5e73ade75fa1999ed0dec81de7cb6 Mon Sep 17 00:00:00 2001 From: Russ Cox Date: Mon, 19 Jan 2015 13:24:43 -0500 Subject: [dev.cc] liblink: invoke 'go tool objwriter' to implement writeobj, if directed This CL enables moving the bulk of the object writing code out of liblink and into translated Go libraries in cmd/internal/obj, but it does not do the move. This CL introduces two new environment variables, $GOOBJ and $GOOBJWRITER, but both will be deleted along with the rest of the liblink C code. The default behavior of a build is unchanged by this CL: the C version of liblink uses the C object layout and writing code. If $GOOBJ=1, liblink invokes go tool objwriter instead. If $GOOBJ=2, liblink does its own layout and then invokes go tool objwriter, which checks that it gets the same answer. That is, in $GOOBJ=2 mode, both the C and the Go version of the code run, and the operation fails if the two produce different answers. This provides a very strong check that the translation is working correctly. Change-Id: I56ab49b07ccb2c7b81085f1d6950131047c6aa3c Reviewed-on: https://go-review.googlesource.com/3048 Reviewed-by: Ian Lance Taylor --- src/liblink/objfile.c | 52 +++++++++++++++++++++++++++++++++------------------ 1 file changed, 34 insertions(+), 18 deletions(-) (limited to 'src/liblink/objfile.c') diff --git a/src/liblink/objfile.c b/src/liblink/objfile.c index 6711aaf776..8c2257de8a 100644 --- a/src/liblink/objfile.c +++ b/src/liblink/objfile.c @@ -119,29 +119,45 @@ static char *rdstring(Biobuf*); static void rddata(Biobuf*, uchar**, int*); static LSym *rdsym(Link*, Biobuf*, char*); -void writeobjdirect(Link*, Biobuf*); +void writeobjdirect(Link *ctxt, Biobuf *b); + +void writeobjgo1(Link*, char*); +void writeobjgo2(Link*, char*, int64); + +extern char *outfile; void writeobj(Link *ctxt, Biobuf *b) { - char *cmd[3]; - - // TODO(rsc): Use 'go tool objwriter' to write object file, - // allowing the bulk of liblink to be moved into Go. - // As a first step, we check that we can invoke objwriter at all - // (it is an empty program for now). - // This tests the cmd/dist bootstrap process, making sure - // that objwriter is available when it needs to be. - // Once the support mechanisms are there, we can put the - // real code in. - - cmd[0] = smprint("%s/pkg/tool/%s_%s/objwriter", getgoroot(), getgohostos(), getgohostarch()); - cmd[1] = "ping"; - cmd[2] = nil; - if(runcmd(cmd) < 0) - sysfatal("cannot run objwriter: %r"); + vlong start; + char *env; + + // If $GOOBJ > 0, invoke the Go version of the liblink + // output routines via a subprocess. + // If $GOOBJ == 1, copy that subprocess's output to + // the actual output file. + // If $GOOBJ >= 2, generate output using the usual C version + // but then check that the subprocess wrote the same bytes. + // $GOOBJ is a temporary setting for the transition to a + // Go liblink back end. Once the C liblink back ends are deleted, + // we will hard code the GOOBJ=1 behavior. + env = getenv("GOOBJ"); + if(env == nil) + env = "2"; + if(atoi(env) == 0) { + writeobjdirect(ctxt, b); + return; + } - writeobjdirect(ctxt, b); + Bflush(b); + start = Boffset(b); + writeobjgo1(ctxt, outfile); + if(atoi(env) > 1) { + writeobjdirect(ctxt, b); + Bflush(b); + } + writeobjgo2(ctxt, outfile, start); + Bseek(b, 0, 2); } // The Go and C compilers, and the assembler, call writeobj to write -- cgit v1.3-5-g9baa