why would I get a segmentation fault on one system but not the other?

[jd1008]

On 02/22/2015 06:11 PM, David Benfell wrote:
> On Mon, Feb 23, 2015 at 12:14:33AM +0000, Ken Moffat wrote:
>
> <mutt failed to include text>
>
> Hmmm, don't know why your suggestion didn't appear. First the old
> machine:
>
> [benfell at home ~]% grep Features /var/run/dmesg.boot
>    Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
>    Features2=0x7fdafbbf<SSE3,PCLMULQDQ,DTES64,MON,DS_CPL,VMX,EST,TM2,SSSE3,<b11>,FMA,CX16,xTPR,PDCM,PCID,SSE4.1,SSE4.2,MOVBE,POPCNT,TSCDLT,AESNI,XSAVE,OSXSAVE,AVX,F16C,RDRAND>
>    AMD Features=0x2c100800<SYSCALL,NX,Page1GB,RDTSCP,LM>
>    AMD Features2=0x21<LAHF,ABM>
>    Structured Extended
> Features=0x27ab<FSGSBASE,TSCADJ,BMI1,AVX2,SMEP,BMI2,ERMS,INVPCID>
>    XSAVE Features=0x1<XSAVEOPT>
>    Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
>    Features2=0x7fdafbbf<SSE3,PCLMULQDQ,DTES64,MON,DS_CPL,VMX,EST,TM2,SSSE3,<b11>,FMA,CX16,xTPR,PDCM,PCID,SSE4.1,SSE4.2,MOVBE,POPCNT,TSCDLT,AESNI,XSAVE,OSXSAVE,AVX,F16C,RDRAND>
>    AMD Features=0x2c100800<SYSCALL,NX,Page1GB,RDTSCP,LM>
>    AMD Features2=0x21<LAHF,ABM>
>    Structured Extended
> Features=0x27ab<FSGSBASE,TSCADJ,BMI1,AVX2,SMEP,BMI2,ERMS,INVPCID>
>    XSAVE Features=0x1<XSAVEOPT>
>
> Now the newer machine:
>
> vegan# grep Features /var/run/dmesg.boot
>    Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
>    Features2=0x7ffafbff<SSE3,PCLMULQDQ,DTES64,MON,DS_CPL,VMX,SMX,EST,TM2,SSSE3,<b11>,FMA,CX16,xTPR,PDCM,PCID,SSE4.1,SSE4.2,x2APIC,MOVBE,POPCNT,TSCDLT,AESNI,XSAVE,OSXSAVE,AVX,F16C,RDRAND>
>    AMD Features=0x2c100800<SYSCALL,NX,Page1GB,RDTSCP,LM>
>    AMD Features2=0x21<LAHF,ABM>
>    Structured Extended
> Features=0x27ab<FSGSBASE,TSCADJ,BMI1,AVX2,SMEP,BMI2,ERMS,INVPCID>
>    XSAVE Features=0x1<XSAVEOPT>
>    Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
>    Features2=0x7ffafbff<SSE3,PCLMULQDQ,DTES64,MON,DS_CPL,VMX,SMX,EST,TM2,SSSE3,<b11>,FMA,CX16,xTPR,PDCM,PCID,SSE4.1,SSE4.2,x2APIC,MOVBE,POPCNT,TSCDLT,AESNI,XSAVE,OSXSAVE,AVX,F16C,RDRAND>
>    AMD Features=0x2c100800<SYSCALL,NX,Page1GB,RDTSCP,LM>
>    AMD Features2=0x21<LAHF,ABM>
>    Structured Extended
> Features=0x27ab<FSGSBASE,TSCADJ,BMI1,AVX2,SMEP,BMI2,ERMS,INVPCID>
>    XSAVE Features=0x1<XSAVEOPT>
>
> This all Greek to me. Perhaps a diff will help:
>
> [benfell at vegan ~]% diff -u Features.home Features.vegan
> --- Features.home       2015-02-22 17:09:32.000000000 -0800
> +++ Features.vegan      2015-02-22 17:09:01.000000000 -0800
> @@ -1,15 +1,13 @@
> -[benfell at home ~]% grep Features /var/run/dmesg.boot
> +vegan# grep Features /var/run/dmesg.boot
>     Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
> -  Features2=0x7fdafbbf<SSE3,PCLMULQDQ,DTES64,MON,DS_CPL,VMX,EST,TM2,SSSE3,<b11>,FMA,CX16,xTPR,PDCM,PCID,SSE4.1,SSE4.2,MOVBE,POPCNT,TSCDLT,AESNI,XSAVE,OSXSAVE,AVX,F16C,RDRAND>
> +
> Features2=0x7ffafbff<SSE3,PCLMULQDQ,DTES64,MON,DS_CPL,VMX,SMX,EST,TM2,SSSE3,<b11>,FMA,CX16,xTPR,PDCM,PCID,SSE4.1,SSE4.2,x2APIC,MOVBE,POPCNT,TSCDLT,AESNI,XSAVE,OSXSAVE,AVX,F16C,RDRAND>
>     AMD Features=0x2c100800<SYSCALL,NX,Page1GB,RDTSCP,LM>
>     AMD Features2=0x21<LAHF,ABM>
> -  Structured Extended
> -Features=0x27ab<FSGSBASE,TSCADJ,BMI1,AVX2,SMEP,BMI2,ERMS,INVPCID>
> +  Structured Extended
> Features=0x27ab<FSGSBASE,TSCADJ,BMI1,AVX2,SMEP,BMI2,ERMS,INVPCID>
>     XSAVE Features=0x1<XSAVEOPT>
>     Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
> -  Features2=0x7fdafbbf<SSE3,PCLMULQDQ,DTES64,MON,DS_CPL,VMX,EST,TM2,SSSE3,<b11>,FMA,CX16,xTPR,PDCM,PCID,SSE4.1,SSE4.2,MOVBE,POPCNT,TSCDLT,AESNI,XSAVE,OSXSAVE,AVX,F16C,RDRAND>
> +
> Features2=0x7ffafbff<SSE3,PCLMULQDQ,DTES64,MON,DS_CPL,VMX,SMX,EST,TM2,SSSE3,<b11>,FMA,CX16,xTPR,PDCM,PCID,SSE4.1,SSE4.2,x2APIC,MOVBE,POPCNT,TSCDLT,AESNI,XSAVE,OSXSAVE,AVX,F16C,RDRAND>
>     AMD Features=0x2c100800<SYSCALL,NX,Page1GB,RDTSCP,LM>
>     AMD Features2=0x21<LAHF,ABM>
> -  Structured Extended
> -Features=0x27ab<FSGSBASE,TSCADJ,BMI1,AVX2,SMEP,BMI2,ERMS,INVPCID>
> +  Structured Extended
> Features=0x27ab<FSGSBASE,TSCADJ,BMI1,AVX2,SMEP,BMI2,ERMS,INVPCID>
>     XSAVE Features=0x1<XSAVEOPT>
>
> Thanks!
Well, I see this fundamental difference:


<Features2=0x7ffafbff<SSE3,PCLMULQDQ,DTES64,MON,DS_CPL,VMX,SMX,EST,TM2,SSSE3,<b11>,FMA,CX16,xTPR,PDCM,PCID,SSE4.1,SSE4.2,x2APIC,MOVBE,POPCNT,TSCDLT,AESNI,XSAVE,OSXSAVE,AVX,F16C,RDRAND>

 >Features2=0x7fdafbbf<SSE3,PCLMULQDQ,DTES64,MON,DS_CPL,VMX, 
,EST,TM2,SSSE3,<b11>,FMA,CX16,xTPR,PDCM,PCID,SSE4.1,SSE4.2, 
,MOVBE,POPCNT,TSCDLT,AESNI,XSAVE,OSXSAVE,AVX,F16C,RDRAND>

The 2nd line is lacking cpu features SMX and x2APIC
I have not dabbled in compilers for many years, but one OP already mentioned
the possibility of differences in AMD 64 architecture instruction 
generation by the C compiler.