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Re: [PATCH elfutils 2/2] [tests] parse inode in /proc/pid/maps correctly in run-backtrace-data.sh
- From: Mark Wielaard <mark at klomp dot org>
- To: Yonghong Song <yhs at fb dot com>
- Cc: elfutils-devel at sourceware dot org, ast at fb dot com
- Date: Tue, 29 Jan 2019 21:50:12 +0100
- Subject: Re: [PATCH elfutils 2/2] [tests] parse inode in /proc/pid/maps correctly in run-backtrace-data.sh
- References: <email@example.com> <firstname.lastname@example.org>
On Fri, Jan 25, 2019 at 01:20:09PM -0800, Yonghong Song wrote:
> The backtrace-data.c parsed the inode in /proc/pid/maps with
> format "%*x".
> This caused failure if inode is big. For example,
> 7f269223d000-7f269226b000 r-xp 00000000 00:50 10224326387095067468 /home/...
I have a bit of trouble replicating this (with a simple sscanf).
How exactly does it fail?
> The correct format should be "%*lu" to reflect inode "unsigned long" type.
> But that caused the following compilation error.
> acktrace-data.c: In function ‘maps_lookup’:
> backtrace-data.c:109:22: error: use of assignment suppression and length modifier
> together in gnu_scanf format [-Werror=format=]
> i = fscanf (f, "%lx-%lx %*s %lx %*x:%*x %*lu", &start, &end, &offset);
Not that it matters much, since we are really ignoring the rest of the
line and this is just a test. But I do wonder why %*u doesn't work.
The warning says you cannot combine a length specifier with
a ignored format specifier. Which kind of makes sense given that the
length is for the variable to assign the value for, not the format.
So it seems $*u should do the trick. But since I haven't been able
to make the original fail, I might be wrong.