Bug ID: JDK-8046408 Build failure from multiple ptrace.h

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JDK 8	JDK 9
8u20Fixed	9 b22Fixed

"I" in the following is kim.barrett@oracle.com.  I don't have a JIRA account yet.

Attempting to build jdk9/dev on SuSE 13.1, I encountered the following build error:

In file included from /home/kab/sandboxes/kab-test/hotspot/agent/src/os/linux/libproc.h:37:0,
                 from /home/kab/sandboxes/kab-test/hotspot/agent/src/os/linux/libproc_impl.h:30,
                 from /home/kab/sandboxes/kab-test/hotspot/agent/src/os/linux/ps_proc.c:33:
/usr/include/linux/ptrace.h:58:8: error: redefinition of ���struct ptrace_peeksiginfo_args���
 struct ptrace_peeksiginfo_args {
        ^
In file included from /home/kab/sandboxes/kab-test/hotspot/agent/src/os/linux/ps_proc.c:32:0:
/usr/include/sys/ptrace.h:191:8: note: originally defined here
 struct ptrace_peeksiginfo_args
        ^

The problem is that ps_proc.c is directly including <sys/ptrace.h> and indirect including <linux/ptrace.h> (via "libproc.h"), and they appear to be incompatible on the system in question.  A bit of web searches would seem to indicate that including both is generally not a good idea.  For example, linux/ptrace.h defines as macros some names that sys/ptrace.h defines as enum constants.  An include order of linux/ptrace.h first then sys/ptrace.h likely results in lots of syntax errors.

The include of <linux/ptrace.h> was added here:
  mikael c884ec3ea87f Tue Apr 29 22:05:10 2014 -0700: #include <linux/ptrace.h>

I'm not sure why I'm getting a compiler error here but presumably most other folks are not.  It may have something to do with the combination of compiler version (g++4.8.1).

Changing hotspot/agent/src/os/linux/libproc.h to include <sys/ptrace.h> rather than <linux/ptrace.h> eliminated the error for me, and allowed my build to run.

There are two ptrace.h headers available for linux, <sys/ptrace.h> and <linux/ptrace.h>. A new struct (ptrace_peeksiginfo_args) was recently added to each, but the addition in <sys/ptrace.h> didn't follow the convention there of using a double-underscore prefix for type names declared in that file. As a result, if both headers are included (as is occurring in our code), there are multiple definitions of that struct. It appears to be a "well known" problem that already has a fix [1], but glibc 2.18 was released with this problem. The inclusion of both variants is due to a file (ps_proc.c) directly including <sys/ptrace.h> and indirectly including <linux/ptrace.h>, where the indirectly including header is used in other places that don't include <sys/ptrace.h>. Our code can presently use either of the headers. The number of affected system configurations is likely small, but this is easy to fix. Proposed change is to prefer <sys/ptrace.h> rather than <linux/ptrace.h>. I've submitted a patch. [1] https://www.sourceware.org/ml/libc-alpha/2014-01/msg00078.html

13-06-2014