cmd/ld: steps toward 386 host linking

- Introduce MaxAlign constant and use in data layout
and ELF section header.

- Allow up to 16-byte alignment for large objects
(will help Keith's hash changes).

- Emit ELF symbol for .rathole (global /dev/null used by 8c).

- Invoke gcc with -m32/-m64 as appropriate.

- Don't invoke gcc if writing the .o file failed.

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/7563045

2 files changed, 5 insertions, 0 deletions

diff --git a/src/cmd/8l/l.h b/src/cmd/8l/l.h
index 062dc05662..f6de746466 100644
--- a/src/cmd/8l/l.h
+++ b/src/cmd/8l/l.h
@@ -42,6 +42,7 @@ enum
 	thechar = '8',
 	PtrSize = 4,
 	IntSize = 4,
+	MaxAlign = 32,	// max data alignment
 	FuncAlign = 16
 };
 
diff --git a/src/cmd/8l/obj.c b/src/cmd/8l/obj.c
index f06bc5d9dc..8144dfadd0 100644
--- a/src/cmd/8l/obj.c
+++ b/src/cmd/8l/obj.c
@@ -130,6 +130,10 @@ main(int argc, char *argv[])
 	
 	flagparse(&argc, &argv, usage);
 
+	// TODO: link mode flag instead of isobj
+	if(isobj)
+		linkmode = LinkExternal;
+
 	if(argc != 1)
 		usage();