JSON Support configuration breaks usage of caPutLog

[ralphlange]

The JSON Support changes the size of the central data structure that is pushed between users of caPutLog and the caPutLog task, based on a macro value:

caPutLog/caPutLogApp/caPutLogTask.h

Lines 23 to 51 in 079dc77

	typedef union {
	epicsInt8 v_int8;
	epicsUInt8 v_uint8;
	epicsInt16 v_int16;
	epicsUInt16 v_uint16;
	epicsInt32 v_int32;
	epicsUInt32 v_uint32;
	#ifdef DBR_INT64
	epicsInt64 v_int64;
	epicsUInt64 v_uint64;
	#endif
	epicsFloat32 v_float;
	epicsFloat64 v_double;
	char v_string[MAX_STRING_SIZE];
	#if JSON_AND_ARRAYS_SUPPORTED
	epicsInt8 a_int8[MAX_ARRAY_SIZE_BYTES/sizeof(epicsInt8)];
	epicsUInt8 a_uint8[MAX_ARRAY_SIZE_BYTES/sizeof(epicsUInt8)];
	epicsInt16 a_int16[MAX_ARRAY_SIZE_BYTES/sizeof(epicsInt16)];
	epicsUInt16 a_uint16[MAX_ARRAY_SIZE_BYTES/sizeof(epicsUInt16)];
	epicsInt32 a_int32[MAX_ARRAY_SIZE_BYTES/sizeof(epicsInt32)];
	epicsUInt32 a_uint32[MAX_ARRAY_SIZE_BYTES/sizeof(epicsUInt32)];
	epicsInt64 a_int64[MAX_ARRAY_SIZE_BYTES/sizeof(epicsInt64)];
	epicsUInt64 a_uint64[MAX_ARRAY_SIZE_BYTES/sizeof(epicsUInt64)];
	epicsFloat32 a_float[MAX_ARRAY_SIZE_BYTES/sizeof(epicsFloat32)];
	epicsFloat64 a_double[MAX_ARRAY_SIZE_BYTES/sizeof(epicsFloat64)];
	char a_string[MAX_ARRAY_SIZE_BYTES/MAX_STRING_SIZE][MAX_STRING_SIZE];
	#endif
	} VALUE;

That macro is only defined in the local Makefile:

caPutLog/caPutLogApp/Makefile

Lines 30 to 38 in 079dc77

	# Add support for json format and arrays
	# This requires EPICS base version 7.0.1 or higher
	ifdef BASE_7_0
	USR_CPPFLAGS += -DJSON_AND_ARRAYS_SUPPORTED
	caPutLog_SRCS += caPutJsonLogTask.cpp
	caPutLog_SRCS += caPutJsonLogShellCommands.cpp
	INC += caPutJsonLogTask.h
	DBD += caPutJsonLog.dbd
	endif

Any user application that does not define the JSON_AND_ARRAYS_SUPPORTED macro in the same way as the caPutLog module will use a different structure definition and size for sending a log message than the caPutLog module that receives it.

This is wrong. (And not documented.) It will lead to corrupted data, maybe even crashes.

Instead, caPutLog needs to generate a CONFIG snippet that gets included by applications that use the module - allowing the user application always to use the same setting as the module.

[mdavidsaver]

@ralphlange wrt. 477634c , adding caPutLogApp/CONFIG_CAPUTLOG seems excessive considering the simple test ifdef BASE_7_0. And USR_CPPFLAGS += could well cause surprises in dependent module Makefiles. While I see it as bad practice, it is not unknown for such Makfiles to directly assign/overwrite USR_CPPFLAGS =, which would silently loose JSON_AND_ARRAYS_SUPPORTED and lead to a ABI mis-match.

It seems prudent to instead in the header replace the special JSON_AND_ARRAYS_SUPPORTED with a test of EPICS_VERSION from epicsVersion.h.

#include <epicsVersion.h>
...
     char            v_string[MAX_STRING_SIZE]; 
  
#if EPICS_VERSION >= 7
     epicsInt8       a_int8[MAX_ARRAY_SIZE_BYTES/sizeof(epicsInt8)]; 

[mdavidsaver]

Or if you want to continue providing JSON_AND_ARRAYS_SUPPORTED, then simply add at the top of caPutLogTask.h.

#include <epicsVersion.h>
#if EPICS_VERSION >= 7
#  define JSON_AND_ARRAYS_SUPPORTED
#endif

[ralphlange]

I was trying to minimize change in the existing code, but I see your point and agree. Will fix (tomorrow).