[binutils-gdb] gdbserver: Fix incorrect assertion

[Pedro Alves]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=04f0c03a22135c7eefa47ed99c03e5b3dc9a34e2

commit 04f0c03a22135c7eefa47ed99c03e5b3dc9a34e2
Author: Pedro Alves <pedro@palves.net>
Date:   Thu Nov 25 19:07:36 2021 +0000

    gdbserver: Fix incorrect assertion
    
    While playing with adding a new event kind, I noticed that
    prepare_resume_reply TARGET_WAITKIND_FORKED, etc. advance 'buf', so if
    we force-disable the T packet, we'd fail the *buf == 'T' assertion.
    
    Fix it by tweaking the assertion to always look at the beginning of
    the buffer.
    
    Change-Id: I8c38e32353db115edcde418b3b1e8ba12343c22b

Diff:
---
 gdbserver/remote-utils.cc | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/gdbserver/remote-utils.cc b/gdbserver/remote-utils.cc
index 3004130fb25..0599cc9c4f1 100644
--- a/gdbserver/remote-utils.cc
+++ b/gdbserver/remote-utils.cc
@@ -1070,6 +1070,7 @@ prepare_resume_reply (char *buf, ptid_t ptid, const target_waitstatus &status)
       {
 	const char **regp;
 	struct regcache *regcache;
+	char *buf_start = buf;
 
 	if ((status.kind () == TARGET_WAITKIND_FORKED && cs.report_fork_events)
 	    || (status.kind () == TARGET_WAITKIND_VFORKED
@@ -1140,11 +1141,11 @@ prepare_resume_reply (char *buf, ptid_t ptid, const target_waitstatus &status)
 	       An 'S' stop packet always looks like 'Sxx', so all we do
 	       here is convert the buffer from a T packet to an S packet
 	       and the avoid adding any extra content by breaking out.  */
-	    gdb_assert (*buf == 'T');
-	    gdb_assert (isxdigit (*(buf + 1)));
-	    gdb_assert (isxdigit (*(buf + 2)));
+	    gdb_assert (buf_start[0] == 'T');
+	    gdb_assert (isxdigit (buf_start[1]));
+	    gdb_assert (isxdigit (buf_start[2]));
 	    *buf = 'S';
-	    *(buf + 3) = '\0';
+	    buf_start[3] = '\0';
 	    break;
 	  }