format: Add function fdi_name

fadec.h

@@ -135,8 +135,17 @@ int fd_decode(const uint8_t* buf, size_t len, int mode, uintptr_t address,
  **/
 void fd_format(const FdInstr* instr, char* buf, size_t len);
 
+/** Get the stringified name of an instruction type.
+ * \param ty An instruction type
+ * \return The instruction type as string, or "(invalid)".
+ **/
+const char* fdi_name(FdInstrType ty);
 
-/** Gets the type/mnemonic of the instruction. **/
+
+/** Gets the type/mnemonic of the instruction.
+ * ABI STABILITY NOTE: different versions or builds of the library may use
+ * different values. When linking as shared library, any interpretation of this
+ * value is meaningless; in such cases use  fdi_name. **/
 #define FD_TYPE(instr) ((FdInstrType) (instr)->type)
 /** DEPRECATED: This functionality is obsolete in favor of FD_OT_OFF.
  * Gets the address of the instruction. Invalid if decoded  address == 0. **/

format.c

@@ -19,6 +19,13 @@ static const uint16_t _mnemonic_offs[] = {
 };
 #undef FD_DECODE_TABLE_STRTAB2
 
+const char*
+fdi_name(FdInstrType ty) {
+    if (ty >= sizeof(_mnemonic_offs) / sizeof(_mnemonic_offs[0]))
+        return "(invalid)";
+    return &_mnemonic_str[_mnemonic_offs[ty]];
+}
+
 #define FMT_CONCAT(buf, end, ...) do { \
             buf += snprintf(buf, end - buf, __VA_ARGS__); \
             if (buf > end) \
@@ -45,7 +52,7 @@ fd_format(const FdInstr* instr, char* buffer, size_t len)
     if (FD_HAS_LOCK(instr))
         FMT_CONCAT(buf, end, "lock:");
 
-    FMT_CONCAT(buf, end, "%s", &_mnemonic_str[_mnemonic_offs[FD_TYPE(instr)]]);
+    FMT_CONCAT(buf, end, "%s", fdi_name(FD_TYPE(instr)));
     if (FD_OPSIZE(instr))
         FMT_CONCAT(buf, end, "_%u", FD_OPSIZE(instr));