Fix error condition for SC and CS

The SC and CS PDF operators correctly checked the return code from the
underlying setcolor and setcolorspace code, but we had already
set up the exec stack for handling a non-error return.

We have to do this before calling the underlying code, as that also
uses a state machine, and alters the exec stack. We must push our
own execution context first.

Ordinarily this isn't a problem, but if we have a custom error handler
which doesn't stop the interpreter, then we would continue on to try
and use what we'd pushed onto the exec stack, with predictably dire
results.

Here we avoid this by saving the exec stack pointer on entry, and if
an error occurs, restoring back to that point before returning control
to the PostScript interpreter.

A minor point, but we now also reset the space/color on an error as
well, previously it would have been left with the wrong space set.

1 files changed, 8 insertions, 0 deletions

diff --git a/psi/zcolor.c b/psi/zcolor.c
index e27baf988..853cee1eb 100644
--- a/psi/zcolor.c
+++ b/psi/zcolor.c
@@ -6611,6 +6611,7 @@ static int
 zsetstrokecolor(i_ctx_t * i_ctx_p)
 {
     int code;
+    es_ptr iesp = esp;  /* preserve exec stack in case of error */
 
     code = zswapcolors(i_ctx_p);
     if (code < 0)
@@ -6627,6 +6628,9 @@ zsetstrokecolor(i_ctx_t * i_ctx_p)
     if (code >= 0)
         return o_push_estack;
 
+    /* Something went wrong, swap back to the non-stroking colour and restore the exec stack */
+    esp = iesp;
+    (void)zswapcolors(i_ctx_p);
     return code;
 }
 static int
@@ -6638,6 +6642,7 @@ static int
 zsetstrokecolorspace(i_ctx_t * i_ctx_p)
 {
     int code;
+    es_ptr iesp = esp;  /* preserve exec stack in case of error */
 
     code = zswapcolors(i_ctx_p);
     if (code < 0)
@@ -6653,6 +6658,9 @@ zsetstrokecolorspace(i_ctx_t * i_ctx_p)
     if (code >= 0)
         return o_push_estack;
 
+    /* Something went wrong, swap back to the non-stroking space and restore the exec stack */
+    esp = iesp;
+    (void)zswapcolors(i_ctx_p);
     return code;
 }