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Date: Tue, 14 Oct 2014 10:17:34 +0800
From: "bobodog" <8192542@...com>
To: "musl" <musl@...ts.openwall.com>
Subject: [math] The math library have some bug for ceil,floor,round functioin, in arm mode

HI,ALL
         We use musl in arm process, but found some bugs about math library,  x86 process is ok!


         Here the test result:
         1) In ARM mode: (the result is wrong)


[    9.235921][kernel/command/cmd-test.c:44] ceil(-0.125000) = 0.000000, floor(-0.125000) = -1.000000, round(-0.125000) = 0.000000
[    9.238523][kernel/command/cmd-test.c:44] ceil(-0.250000) = 0.000000, floor(-0.250000) = -1.000000, round(-0.250000) = 0.000000
[    9.239770][kernel/command/cmd-test.c:44] ceil(-0.375000) = 0.000000, floor(-0.375000) = -1.000000, round(-0.375000) = 0.000000
[    9.241081][kernel/command/cmd-test.c:44] ceil(-0.500000) = 0.000000, floor(-0.500000) = -1.000000, round(-0.500000) = -0.500000
[    9.242361][kernel/command/cmd-test.c:44] ceil(-0.625000) = 0.000000, floor(-0.625000) = -1.000000, round(-0.625000) = -0.625000
[    9.243637][kernel/command/cmd-test.c:44] ceil(-0.750000) = 0.000000, floor(-0.750000) = -1.000000, round(-0.750000) = -0.750000
[    9.244879][kernel/command/cmd-test.c:44] ceil(-0.875000) = 0.000000, floor(-0.875000) = -1.000000, round(-0.875000) = -0.875000
[    9.246183][kernel/command/cmd-test.c:44] ceil(-1.000000) = -1.000000, floor(-1.000000) = -1.000000, round(-1.000000) = -1.000000
[    9.247457][kernel/command/cmd-test.c:44] ceil(-1.125000) = -1.125000, floor(-1.125000) = -1.125000, round(-1.125000) = -1.125000
[    9.248333][kernel/command/cmd-test.c:44] ceil(-1.250000) = -1.250000, floor(-1.250000) = -1.250000, round(-1.250000) = -1.250000
[    9.249303][kernel/command/cmd-test.c:44] ceil(-1.375000) = -1.375000, floor(-1.375000) = -1.375000, round(-1.375000) = -1.375000
[    9.250456][kernel/command/cmd-test.c:44] ceil(-1.500000) = -1.500000, floor(-1.500000) = -1.500000, round(-1.500000) = -1.500000
[    9.251730][kernel/command/cmd-test.c:44] ceil(-1.625000) = -1.625000, floor(-1.625000) = -1.625000, round(-1.625000) = -1.625000
[    9.252975][kernel/command/cmd-test.c:44] ceil(-1.750000) = -1.750000, floor(-1.750000) = -1.750000, round(-1.750000) = -1.750000
[    9.254272][kernel/command/cmd-test.c:44] ceil(-1.875000) = -1.875000, floor(-1.875000) = -1.875000, round(-1.875000) = -1.875000
[    9.255563][kernel/command/cmd-test.c:44] ceil(-2.000000) = -2.000000, floor(-2.000000) = -2.000000, round(-2.000000) = -2.000000
[    9.256813][kernel/command/cmd-test.c:44] ceil(-2.125000) = -2.125000, floor(-2.125000) = -2.125000, round(-2.125000) = -2.125000
[    9.257610][kernel/command/cmd-test.c:44] ceil(-2.250000) = -2.250000, floor(-2.250000) = -2.250000, round(-2.250000) = -2.250000
[    9.258029][kernel/command/cmd-test.c:44] ceil(-2.375000) = -2.375000, floor(-2.375000) = -2.375000, round(-2.375000) = -2.375000
[    9.259500][kernel/command/cmd-test.c:44] ceil(-2.500000) = -2.500000, floor(-2.500000) = -2.500000, round(-2.500000) = -2.500000
‍

         2) In X86 mode: (the result is correct)
[    3.790000][kernel/command/cmd-test.c:44] ceil(-0.125000) = 0.000000, floor(-0.125000) = -1.000000, round(-0.125000) = 0.000000
[    3.790000][kernel/command/cmd-test.c:44] ceil(-0.250000) = 0.000000, floor(-0.250000) = -1.000000, round(-0.250000) = 0.000000
[    3.790000][kernel/command/cmd-test.c:44] ceil(-0.375000) = 0.000000, floor(-0.375000) = -1.000000, round(-0.375000) = 0.000000
[    3.790000][kernel/command/cmd-test.c:44] ceil(-0.500000) = 0.000000, floor(-0.500000) = -1.000000, round(-0.500000) = -1.000000
[    3.790000][kernel/command/cmd-test.c:44] ceil(-0.625000) = 0.000000, floor(-0.625000) = -1.000000, round(-0.625000) = -1.000000
[    3.790000][kernel/command/cmd-test.c:44] ceil(-0.750000) = 0.000000, floor(-0.750000) = -1.000000, round(-0.750000) = -1.000000
[    3.790000][kernel/command/cmd-test.c:44] ceil(-0.875000) = 0.000000, floor(-0.875000) = -1.000000, round(-0.875000) = -1.000000
[    3.790000][kernel/command/cmd-test.c:44] ceil(-1.000000) = -1.000000, floor(-1.000000) = -1.000000, round(-1.000000) = -1.000000
[    3.790000][kernel/command/cmd-test.c:44] ceil(-1.125000) = -1.000000, floor(-1.125000) = -2.000000, round(-1.125000) = -1.000000
[    3.790000][kernel/command/cmd-test.c:44] ceil(-1.250000) = -1.000000, floor(-1.250000) = -2.000000, round(-1.250000) = -1.000000
[    3.790000][kernel/command/cmd-test.c:44] ceil(-1.375000) = -1.000000, floor(-1.375000) = -2.000000, round(-1.375000) = -1.000000
[    3.790000][kernel/command/cmd-test.c:44] ceil(-1.500000) = -1.000000, floor(-1.500000) = -2.000000, round(-1.500000) = -2.000000
[    3.790000][kernel/command/cmd-test.c:44] ceil(-1.625000) = -1.000000, floor(-1.625000) = -2.000000, round(-1.625000) = -2.000000
[    3.790000][kernel/command/cmd-test.c:44] ceil(-1.750000) = -1.000000, floor(-1.750000) = -2.000000, round(-1.750000) = -2.000000
[    3.790000][kernel/command/cmd-test.c:44] ceil(-1.875000) = -1.000000, floor(-1.875000) = -2.000000, round(-1.875000) = -2.000000
[    3.790000][kernel/command/cmd-test.c:44] ceil(-2.000000) = -2.000000, floor(-2.000000) = -2.000000, round(-2.000000) = -2.000000
[    3.790000][kernel/command/cmd-test.c:44] ceil(-2.125000) = -2.000000, floor(-2.125000) = -3.000000, round(-2.125000) = -2.000000
[    3.790000][kernel/command/cmd-test.c:44] ceil(-2.250000) = -2.000000, floor(-2.250000) = -3.000000, round(-2.250000) = -2.000000
[    3.790000][kernel/command/cmd-test.c:44] ceil(-2.375000) = -2.000000, floor(-2.375000) = -3.000000, round(-2.375000) = -2.000000
[    3.790000][kernel/command/cmd-test.c:44] ceil(-2.500000) = -2.000000, floor(-2.500000) = -3.000000, round(-2.500000) = -3.000000


        The test code:
int test(int argc, char ** argv)
{
	double n = 0.0;
	int i;


	for(i = 0; i < 20; i++)
	{
		n = n - 0.125;
		printf("ceil(%f) = %f, floor(%f) = %f, round(%f) = %f\n", n, ceil(n), n, floor(n), n, round(n));
	}


	return 0;
}‍


       May be rint trunc have same problem. this is supper big bug!!!


------------------
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蒋建军                            
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