perf expr: Fix memory leaks in metric bison

Add a destructor for strings to reclaim memory in the event of errors.
Free the ID given for a lookup, it was previously strdup-ed in the lex
code.
Signed-off-by: Ian Rogers <irogers@google.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20200513000318.15166-1-irogers@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/expr.y

@@ -27,6 +27,7 @@
 %token EXPR_PARSE EXPR_OTHER EXPR_ERROR
 %token <num> NUMBER
 %token <str> ID
+%destructor { free ($$); } <str>
 %token MIN MAX IF ELSE SMT_ON
 %left MIN MAX IF
 %left '|'
@@ -94,8 +95,10 @@ if_expr:
 expr:	  NUMBER
 	| ID			{ if (lookup_id(ctx, $1, &$$) < 0) {
 					pr_debug("%s not found\n", $1);
+					free($1);
 					YYABORT;
 				  }
+				  free($1);
 				}
 	| expr '|' expr		{ $$ = (long)$1 | (long)$3; }
 	| expr '&' expr		{ $$ = (long)$1 & (long)$3; }