Change in flashrom[master]: programmer.h: Convert anon union to anon struct

[Edward O'Callaghan (Code Review)]

Edward O'Callaghan has submitted this change. ( https://review.coreboot.org/c/flashrom/+/50246 )

Change subject: programmer.h: Convert anon union to anon struct
......................................................................

programmer.h: Convert anon union to anon struct

Convert the anon union of registered masters in the mst
field of the flashctx to a anon struct. If we are going
to dereference a pointer there in an undefined way we
should crash and not plow ahead with invalid memory.

The user of the registered_masters type is therefore
responsible for querying the buses_supported field before
attempting to dereference a ptr field in the anon struct.

BUG=b:175849641
TEST=`flashrom -p internal --flash-name`

Change-Id: I576967a8599b923c902e39f177f39146291cc242
Signed-off-by: Edward O'Callaghan 
Reviewed-on: https://review.coreboot.org/c/flashrom/+/50246
Reviewed-by: Anastasia Klimchuk 
Reviewed-by: Peter Marheine 
Reviewed-by: Daniel Campello 
Reviewed-by: Sam McNally 
Tested-by: build bot (Jenkins) 
---
M opaque.c
M programmer.c
M programmer.h
M spi.c
4 files changed, 5 insertions(+), 4 deletions(-)

Approvals:
  build bot (Jenkins): Verified
  Sam McNally: Looks good to me, approved
  Daniel Campello: Looks good to me, but someone else must approve
  Peter Marheine: Looks good to me, but someone else must approve
  Anastasia Klimchuk: Looks good to me, but someone else must approve

diff --git a/opaque.c b/opaque.c
index 276934f..e3103c8 100644
--- a/opaque.c
+++ b/opaque.c
@@ -48,7 +48,7 @@

int register_opaque_master(const struct opaque_master *mst)
 {
-	struct registered_master rmst;
+	struct registered_master rmst = {0};

if (!mst->probe || !mst->read || !mst->write || !mst->erase) {
    	msg_perr("%s called with incomplete master definition. "
diff --git a/programmer.c b/programmer.c
index bee60e3..42ea2e3 100644
--- a/programmer.c
+++ b/programmer.c
@@ -83,7 +83,8 @@
 int register_par_master(const struct par_master *mst,
    		    const enum chipbustype buses)
 {
-	struct registered_master rmst;
+	struct registered_master rmst = {0};
+
    if (!mst->chip_writeb || !mst->chip_writew || !mst->chip_writel ||
        !mst->chip_writen || !mst->chip_readb || !mst->chip_readw ||
        !mst->chip_readl || !mst->chip_readn) {
diff --git a/programmer.h b/programmer.h
index 29a100b..675a259 100644
--- a/programmer.h
+++ b/programmer.h
@@ -749,7 +749,7 @@
 int register_par_master(const struct par_master *mst, const enum chipbustype buses);
 struct registered_master {
    enum chipbustype buses_supported;
-	union {
+	struct {
    	struct par_master par;
    	struct spi_master spi;
    	struct opaque_master opaque;
diff --git a/spi.c b/spi.c
index aed2a92..aa245d7 100644
--- a/spi.c
+++ b/spi.c
@@ -133,7 +133,7 @@

int register_spi_master(const struct spi_master *mst)
 {
-	struct registered_master rmst;
+	struct registered_master rmst = {0};

if (!mst->write_aai || !mst->write_256 || !mst->read || !mst->command ||
        !mst->multicommand ||