[dpdk-dev] [PATCH v5] eal_common_cpuflags: Fix %rbx corruption, and simplify the code

[De Lara Guarch, Pablo]

Hi Neil,



>> What was the value of RTE_COMPILE_TIME_CPUFLAGS when you built your library?  If you added defines for flag support that are not tested for yet in the cpu_feature_table, that would be the error you would see I think



>RTE_COMPILE_TIME_CPUFLAGS= >RTE_CPUFLAG_SSE,RTE_CPUFLAG_SSE2,RTE_CPUFLAG_SSE3,RTE_CPUFLAG_SSSE3,RTE_CPUFLAG_SSE4_1,RTE_CPUFLAG_SSE4_2,RTE_CPUFLAG_AES,RTE_CPUFLAG_PCLMULQDQ,RTE_CPUFLAG_AVX



>For gcc_version >=4.6, that value is the same, of course (and all those flags are supported). So it has to be something else...



Silly me, I just saw what was hapenning. There are two missing brackets in the loop:



for (i = 0; i < sizeof(compile_time_flags)/sizeof(compile_time_flags[0]); i++) {

ret = rte_cpu_get_flag_enabled(compile_time_flags[i]);



if (ret < 0) {

fprintf(stderr,

  "ERROR: CPU feature flag lookup failed with error %d\n",

  ret);

exit(1);

}

if (!ret) {

fprintf(stderr,

  "ERROR: This system does not support \"%s\".\n"

  "Please check that RTE_MACHINE is set correctly.\n",

  cpu_feature_table[compile_time_flags[i]].name);

exit(1);

}

}



So, basically, "i" was size of the array +1 after the loop and only the return value was being checked for the last item. Not sure why higher versions of gcc do not catch this.



Thanks,



Pablo de Lara

DPDK SW Engineer



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