headers: Add macro to print error code as string

[pdxjohnny]

• Adds a PRINT_SGX_STATUS macro to sgx_error.h which prints
  the sgx_status_t as a string.

[pdxjohnny]

Generated with:

(
echo -e '#define PRINT_SGX_STATUS(FILE_STRUCT, STATUS_T) \\\n    switch (STATUS_T) {\\';
for error in $(grep -E '=.*SGX_MK_ERROR' /opt/intel/sgxsdk/include/sgx_error.h | awk '{print $1}' | sed 's/=//g'); do
  printf '    case %s:\\\n        fprintf(FILE_STRUCT, "Error: %s\\n");\\\n        break;\\\n' $error $error;
done;
echo -e '    }'
)

[pdxjohnny]

maybe this would be better as something similar to perror called sgx_perror or something. Where it acts just as perror does but for sgx_status_t errors

[sergefdrv]

Might be even better to make it similar to strerror, for fine control of output. Think of advanced logging mechanism.

[pdxjohnny]

Ya that is probably a better option, I think that's what was started in #346 perhaps that PR should be one PR introducing the strerror and another adding the logging to various places.

[pdxjohnny]

Something similar is going on in the examples

linux-sgx/SampleCode/SampleEnclave/App/App.cpp

Lines 55 to 70 in a85fbe9

	static sgx_errlist_t sgx_errlist[] = {
	{
	SGX_ERROR_UNEXPECTED,
	"Unexpected error occurred.",
	NULL
	},
	{
	SGX_ERROR_INVALID_PARAMETER,
	"Invalid parameter.",
	NULL
	},
	{
	SGX_ERROR_OUT_OF_MEMORY,
	"Out of memory.",
	NULL
	},

[Icaro-Lima]

Hello, I was disinclined to continue working on my pull request after the comment from the Intel member himself saying that maybe it did not help much. And I still maintain my position, I think it is very important and avoids many lines of unnecessary codes that will be inserted in each enclave.

[pdxjohnny]

I agree. As I posted above something similar was done in the sample enclave code. If its useful there then it is of course useful and instead of duplicating that functionality it should be a part of the SDK.

[LuminousXLB]

I believe that it's a really useful patch.
FYI, here's how I did the same thing.

https://pastebin.com/PT4Ds8WQ