Added to C API: adios2_version_struct. adios2_version(adios2_version_…

[pnorbert]

…struct*) and adios2_version_str() functions.
Fixes #3630

[pnorbert]

@vicentebolea: On Linux I get this output mismatch since ADIOS2_VERSION_STR contains the tweak automatically generated by cmake. Can we have another string without it, or generate tweak on all platforms?

$ ./bin/hello_bpWriter_c
ADIOS version as struct 2.9.0
ADIOS version as string 2.9.0.12

[vicentebolea]

Looks good, I proposed a change to remove the dynamic alloc and reduce LoC. I do not feel too strong since this is a utility method, let me know :)

[vicentebolea]

Suggested change

	int patch;
	} adios2_version_struct;
	int patch;
	char str[sizeof(ADIOS2_VERSION_STR)];
	} adios2_version_struct;

[eschnett]

That will not work. This struct has a size that is not known in advance, and it is impossible to call it in a dynamic library. Almost every new version of ADIOS2 will have a different size for this struct, leading to ABI incompatibilities.

Why not use a const char* str field that points to a constant string that does not need to be deallocated?

[vicentebolea]

Suggested change

	char *adios2_version_str(void)
	{
	char *str = (char *)malloc(sizeof(ADIOS2_VERSION_STR));
	snprintf(str, sizeof(ADIOS2_VERSION_STR), ADIOS2_VERSION_STR);
	return str;
	}

[vicentebolea]

Suggested change

	s->patch = ADIOS2_VERSION_PATCH;
	}
	s->patch = ADIOS2_VERSION_PATCH;
	strncpy(s->str, ADIOS2_VERSION_STR, sizeof(ADIOS2_VERSION_STR));
	}

[vicentebolea]

Suggested change

	char *vstr = adios2_version_str();
	printf("ADIOS version as string %s\n", vstr);
	free(vstr);
	printf("ADIOS version as string %s\n", s->str);

[vicentebolea]

Suggested change

	/**
	* Return library version as string in major.minor.patch format
	* String is allocated in the library, must be freed by caller.
	*/
	char *adios2_version_str(void);

[eschnett]

That will not work. This struct has a size that is not known in advance, and it is impossible to call it in a dynamic library. Almost every new version of ADIOS2 will have a different size for this struct, leading to ABI incompatibilities.

Why not use a const char* str field that points to a constant string that does not need to be deallocated?

[eschnett]

It is easier to call functions that don't expect or return a struct. I would prefer

void adios2_version(int *major, int *minor, int *patch);
const char *adios2_version_str(void);

which are overall much simpler to use.

[eschnett]

Another option would be to use global variables, as in

const int adios2_version_major;
const int adios2_version_minor;
const int adios_version_patch;
const char *const adios2_version_str;

[pnorbert]

Remove this pull request for a new one.