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Date: Fri, 11 Apr 2014 11:46:16 +0200
From: Szabolcs Nagy <>
Subject: Re: Preparing for releases 1.1.0 and 1.0.1

* Rich Felker <> [2014-04-10 21:39:11 -0400]:
> On Thu, Apr 10, 2014 at 03:11:23PM +0200, Szabolcs Nagy wrote:
> > * x32 timex is broken (should use long long on x32)
> Uhg, so do we need to move this to bits or do some ugly hack? Or
> rewrite it in the syscall wrapper code like for timespec?

move the struct to bits

> > * math alias issues on non-x86 archs (about +80bytes)
> > (either this or __may_alias__)
> I prefer the +80 bytes; the other may_alias uses are optional and have
> a portable fallback.


> > * use 1/eps for rounding check (with *4 it's nicer, ymmv)
> Could you explain why? I would prefer a change that doesn't require so
> many lines changed since they're all places errors could hide. Just
> getting rid of the CONCAT hack seems preferable to me, but I don't
> mind hearing the reason you like the *4.

well integers are special (eg x87 has fld1) so a bit better code
may be generated and they are more familiar

another way to make the code better on some platforms is to use floats:
(and help valgrind)

diff --git a/src/stdio/vfprintf.c b/src/stdio/vfprintf.c
index f6e7f38..546df28 100644
--- a/src/stdio/vfprintf.c
+++ b/src/stdio/vfprintf.c
@@ -13,8 +13,6 @@
 #define MAX(a,b) ((a)>(b) ? (a) : (b))
 #define MIN(a,b) ((a)<(b) ? (a) : (b))
-#define CONCAT2(x,y) x ## y
-#define CONCAT(x,y) CONCAT2(x,y)
 /* Convenient bit representation for modifier flags, which all fall
  * within 31 codepoints of the space character. */
@@ -343,8 +341,8 @@ static int fmt_fp(FILE *f, long double y, int w, int p, int fl, int t)
 		x = *d % i;
 		/* Are there any significant digits past j? */
 		if (x || d+1!=z) {
-			long double round = CONCAT(0x1p,LDBL_MANT_DIG);
-			long double small;
+			float_t round = 0x1p24f;
+			float_t small;
 			if (*d/i & 1) round += 2;
 			if (x<i/2) small=0x0.8p0;
 			else if (x==i/2 && d+1==z) small=0x1.0p0;
@@ -352,7 +350,12 @@ static int fmt_fp(FILE *f, long double y, int w, int p, int fl, int t)
 			if (pl && *prefix=='-') round*=-1, small*=-1;
 			*d -= x;
 			/* Decide whether to round by probing round+small */
-			if (round+small != round) {
+			/* avoiding compiler bugs */
+			volatile
+			float sum = round+small;
+			if (sum != round) {
 				*d = *d + i;
 				while (*d > 999999999) {

> > * only use nanosec for entropy
> I just worry on some archs with bad timer, this could prevent getting
> sufficiently many temp names (of course the problem already existed).
> Is there more non-valuable entropy we could merge into it? One idea
> was the bytes of struct stat from stat() on /proc/self (this is like
> using pid, but better). But perhaps there's more we could do with just
> time.

stat is ok

if there are different clock sources then you can do more with time
or if we assume the retries take non-predictable time (open syscall
on a crowded /tmp) then that can be measured as well

using the seconds may help a bit

r = ts.tv_sec ^ ts.tv_nsec;

(all the relevant 30bits of r are used so further mixing does not help)

> > * broken legacy header..
> > 
> > diff --git a/include/sys/procfs.h b/include/sys/procfs.h
> > index f7936c4..a1fcabf 100644
> > --- a/include/sys/procfs.h
> > +++ b/include/sys/procfs.h
> > @@ -40,7 +40,7 @@ struct elf_prpsinfo
> >  	char pr_zomb;
> >  	char pr_nice;
> >  	unsigned long int pr_flag;
> > -#if UINTPTR_MAX == 0xffffffff
> > +#if UINTPTR_MAX == 0xffffffff && !defined __powerpc__
> I'm ok with this hack I think.

this is probably still broken on microblaze

my guess is that nobody is actually using this header

> > * linux 3.14 stuff
> > (sched_setattr/sched_getattr syscall numbers, new sockopt flag, new arphdr type)
> This should probably be held until a later release. We need to
> consider ABI issues. I believe we have sufficient room to put a union
> (rather than the kernel's silly non-union approach) over top of our
> schedparam struct and fit all the values needed without ABI breakage,
> but this requires some code to convert to/from the kernel format.

well the kernel did not export any definition for the syscalls
and the sched_attr struct so far, only the syscall numbers

i'm not sure if that was intentional, but currently they cannot
be used reasonably from userspace

> > * makefile/config changes for out-of-tree build
> Last I checked you were still finding breakage in it. When I get done
> with the release and other higher-priority things I'm trying to get
> done, maybe I should look at it and give it a proper review. Sorry I
> haven't gotten around to that yet.

i'd say that there are some tradeoffs..

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