[pushed] Fix aarch64-linux-hw-point.c build problem

[Kevin Buettner]

On Thu, 25 Feb 2021 00:22:52 +0100
Christian Biesinger <cbiesinger@google.com> wrote:

> Since you said nat/aarch64-sve-linux-ptrace.h also includes these headers,
> maybe add the comment there as well?

Done...

Add comment regarding include order of <sys/ptrace.h> and <asm/ptrace.h>

I added the same comment for nat/aarch64-linux-hw-point.c yesterday.
Christian suggested adding the comment for the other file that I had
identified as including both <sys/ptrace.h> and <asm/ptrace.h>.

I searched the sources in gdb/, but found no other files which include
both of these headers.

If possible, I would prefer to see us use <sys/ptrace.h> when possible,
however, from past experience, I've found that this file does not always
contain all of the constants, etc. required by the particular source
file.

gdb/ChangeLog:

	* nat/aarch64-sve-linux-ptrace.h: Add comment regarding include
	order for <sys/ptrace.h> and <asm/ptrace.h>.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 842dc0a1374..7e0b00cc7c6 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2021-02-24  Kevin Buettner  <kevinb@redhat.com>
+
+	* nat/aarch64-sve-linux-ptrace.h: Add comment regarding
+	include order for <sys/ptrace.h> and <asm/ptrace.h>.
+
 2021-02-25  Simon Marchi  <simon.marchi@polymtl.ca>
 
 	PR gdb/26861
diff --git a/gdb/nat/aarch64-sve-linux-ptrace.h b/gdb/nat/aarch64-sve-linux-ptrace.h
index 06684023f5d..be00f306137 100644
--- a/gdb/nat/aarch64-sve-linux-ptrace.h
+++ b/gdb/nat/aarch64-sve-linux-ptrace.h
@@ -22,6 +22,12 @@
 
 #include <signal.h>
 #include <sys/utsname.h>
+
+/* The order in which <sys/ptrace.h> and <asm/ptrace.h> are included
+   can be important.  <sys/ptrace.h> often declares various PTRACE_*
+   enums.  <asm/ptrace.h> often defines preprocessor constants for
+   these very same symbols.  When that's the case, build errors will
+   result when <asm/ptrace.h> is included before <sys/ptrace.h>.  */
 #include <sys/ptrace.h>
 #include <asm/ptrace.h>