x86: return proper error if cs_option() enables AT&T syntax but AT&T support is opt-out at compile time

COMPILE.TXT

@@ -27,7 +27,7 @@ Capstone requires no prerequisite packages, so it is easy to compile & install.
   - CAPSTONE_USE_SYS_DYN_MEM: change this if you have your own dynamic memory management.
   - CAPSTONE_DIET: use this to make the output binaries more compact.
   - CAPSTONE_X86_REDUCE: another option to make X86 binary smaller.
-  - CAPSTONE_X86_ATT_DISABLE: disables AT&T syntax on x86
+  - CAPSTONE_X86_ATT_DISABLE: disables AT&T syntax on x86.
 
   By default, Capstone use system dynamic memory management, and both DIET and X86_REDUCE
   modes are disable.

COMPILE_CMAKE.TXT

@@ -37,7 +37,7 @@ Get CMake for free from http://www.cmake.org.
   - USE_SYS_DYN_MEM: change this to OFF to use your own dynamic memory management.
   - BUILD_DIET: change this to ON to make the binaries more compact.
   - X86_REDUCE: change this to ON to make X86 binary smaller.
-  - X86_ATT_DISABLE: change this to ON to disable AT&T syntax on x86
+  - X86_ATT_DISABLE: change this to ON to disable AT&T syntax on x86.
 
   By default, Capstone use system dynamic memory management, and both DIET and X86_REDUCE
   modes are disabled. To use your own memory allocations, turn ON both DIET &

arch/X86/X86Module.c

@@ -48,6 +48,10 @@ static cs_err option(cs_struct *handle, cs_opt_type type, size_t value)
 				handle->printer = X86_ATT_printInst;
 				handle->syntax = CS_OPT_SYNTAX_ATT;
 				break;
+#elif !defined(CAPSTONE_DIET) && defined(CAPSTONE_X86_ATT_DISABLE)
+				// ATT syntax is unsupported
+				handle->errnum = CS_ERR_X86_ATT;
+				return CS_ERR_X86_ATT;
 #else
 				// this is irrelevant in CAPSTONE_DIET mode
 				handle->errnum = CS_ERR_DIET;

include/capstone.h

@@ -243,6 +243,8 @@ typedef enum cs_err {
 	CS_ERR_VERSION,  // Unsupported version (bindings)
 	CS_ERR_DIET,     // Access irrelevant data in "diet" engine
 	CS_ERR_SKIPDATA, // Access irrelevant data for "data" instruction in SKIPDATA mode
+	CS_ERR_X86_ATT,  // X86 AT&T syntax is unsupported (opt-out at compile time)
+	CS_ERR_X86_INTEL, // X86 Intel syntax is unsupported (opt-out at compile time)
 } cs_err;
 
 /*