From 0d42948f0c822ed3782a45771c8fbc21aa2d6553 Mon Sep 17 00:00:00 2001 From: Andrew Burgess Date: Mon, 24 Apr 2023 15:27:27 +0100 Subject: [PATCH] gdb/doc: extend the documentation of the jump command This commit addresses PR gdb/7946. While checking for bugs relating to the jump command I noticed a long standing bug that points out a deficiency with GDB's documentation of the jump command. The bug points out that 'jump 0x...' is not always the same as 'set $pc = 0x...' and then 'continue'. Writing directly to the $pc register does not update any auxiliary state, e.g. $npc on SPARC, while using 'jump' does. It felt like this would be an easy issue to address by adding a paragraph to the docs, so I took a stab at writing something suitable. Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=7946 Approved-By: Eli Zaretskii --- gdb/doc/gdb.texinfo | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo index d8f7413dc48..263326d54e7 100644 --- a/gdb/doc/gdb.texinfo +++ b/gdb/doc/gdb.texinfo @@ -20618,6 +20618,14 @@ makes the next @code{continue} command or stepping command execute at address @code{0x485}, rather than at the address where your program stopped. @xref{Continuing and Stepping, ,Continuing and Stepping}. +However, writing directly to @code{$pc} will only change the value of +the program-counter register, while using @code{jump} will ensure that +any additional auxiliary state is also updated. For example, on +SPARC, @code{jump} will update both @code{$pc} and @code{$npc} +registers prior to resuming execution. When using the approach of +writing directly to @code{$pc} it is your job to also update the +@code{$npc} register. + The most common occasion to use the @code{jump} command is to back up---perhaps with more breakpoints set---over a portion of a program that has already executed, in order to examine its execution in more -- 2.30.2