[parser] fix semicolon after if statements

If we have two if statements, before the first if statmenet there's no
other statement and between the two stamenets there's another statement,
our parser will complain there's no semicolon after our first if
statement. This commit tries to fix it.

Fixes: #544

CMakeLists.txt

@@ -44,7 +44,7 @@ include_directories(SYSTEM ${LIBELF_INCLUDE_DIRS})
 
 find_package(BISON REQUIRED)
 find_package(FLEX REQUIRED)
-bison_target(bison_parser src/parser.yy ${CMAKE_BINARY_DIR}/parser.tab.cc)
+bison_target(bison_parser src/parser.yy ${CMAKE_BINARY_DIR}/parser.tab.cc VERBOSE)
 flex_target(flex_lexer src/lexer.l ${CMAKE_BINARY_DIR}/lex.yy.cc)
 add_flex_bison_dependency(flex_lexer bison_parser)
 add_library(parser ${BISON_bison_parser_OUTPUTS} ${FLEX_flex_lexer_OUTPUTS})

src/parser.yy

@@ -94,8 +94,8 @@ void yyerror(bpftrace::Driver &driver, const char *s);
 %type <ast::Probe *> probe
 %type <ast::Predicate *> pred
 %type <ast::Ternary *> ternary
-%type <ast::StatementList *> block stmts block_stmts
-%type <ast::Statement *> block_stmt stmt
+%type <ast::StatementList *> block stmts
+%type <ast::Statement *> block_stmt stmt semicolon_ended_stmt
 %type <ast::Expression *> expr
 %type <ast::Call *> call
 %type <ast::Map *> map
@@ -173,19 +173,17 @@ ternary : expr QUES expr COLON expr { $$ = new ast::Ternary($1, $3, $5); }
 param : DOLLAR INT { $$ = new ast::PositionalParameter($2); }
 
 block : "{" stmts "}"     { $$ = $2; }
-      | "{" stmts ";" "}" { $$ = $2; }
       ;
 
-stmts : stmts ";" stmt             { $$ = $1; $1->push_back($3); }
-      | stmts ";" block_stmts stmt { $$ = $1; $1->insert($1->end(), $3->begin(), $3->end()); $1->push_back($4); }
-      | stmts ";" block_stmts      { $$ = $1; $1->insert($1->end(), $3->begin(), $3->end()); }
-      | block_stmts                { $$ = $1; }
+semicolon_ended_stmt: stmt ";"  { $$ = $1; }
+                    ;
+
+stmts : semicolon_ended_stmt stmts { $$ = $2; $2->insert($2->begin(), $1); }
+      | block_stmt stmts           { $$ = $2; $2->insert($2->begin(), $1); }
       | stmt                       { $$ = new ast::StatementList; $$->push_back($1); }
+      |                            { $$ = new ast::StatementList; }
       ;
 
-block_stmts : block_stmts block_stmt     { $$ = $1; $1->push_back($2); }
-            | block_stmt                 { $$ = new ast::StatementList; $$->push_back($1); }
-
 block_stmt : IF "(" expr ")" block  { $$ = new ast::If($3, $5); }
            | IF "(" expr ")" block ELSE block { $$ = new ast::If($3, $5, $7); }
            | UNROLL "(" INT ")" block { $$ = new ast::Unroll($3, $5); }

tests/codegen/if_else_variable.cpp

@@ -6,7 +6,7 @@ namespace codegen {
 
 TEST(codegen, if_else_variable)
 {
-  test("kprobe:f { if (pid > 10000) { $s = 10 } else { $s = 20 }; printf(\"s = %d\", $s) }",
+  test("kprobe:f { if (pid > 10000) { $s = 10 } else { $s = 20 } printf(\"s = %d\", $s) }",
 
 R"EXPECTED(%printf_t = type { i64, i64 }
 

tests/codegen/if_variable.cpp

@@ -6,7 +6,7 @@ namespace codegen {
 
 TEST(codegen, if_variable)
 {
-  test("kprobe:f { if (pid > 10000) { $s = 10 }; printf(\"s = %d\", $s); }",
+  test("kprobe:f { if (pid > 10000) { $s = 10 } printf(\"s = %d\", $s); }",
 
 #if LLVM_VERSION_MAJOR < 6
 R"EXPECTED(%printf_t = type { i64, i64 }

tests/parser.cpp

@@ -381,6 +381,32 @@ TEST(Parser, if_block)
        "     builtin: pid\n");
 }
 
+TEST(Parser, if_stmt_if)
+{
+  test("kprobe:sys_open { if (pid > 10000) { printf(\"%d is high\\n\", pid); } @pid = pid; if (pid < 1000) { printf(\"%d is low\\n\", pid); } }",
+       "Program\n"
+       " kprobe:sys_open\n"
+       "  if\n"
+       "   >\n"
+       "    builtin: pid\n"
+       "    int: 10000\n"
+       "   then\n"
+       "    call: printf\n"
+       "     string: %d is high\\n\n"
+       "     builtin: pid\n"
+       "  =\n"
+       "   map: @pid\n"
+       "   builtin: pid\n"
+       "  if\n"
+       "   <\n"
+       "    builtin: pid\n"
+       "    int: 1000\n"
+       "   then\n"
+       "    call: printf\n"
+       "     string: %d is low\\n\n"
+       "     builtin: pid\n");
+}
+
 TEST(Parser, if_block_variable)
 {
   test("kprobe:sys_open { if (pid > 10000) { $s = 10; } }",
@@ -398,7 +424,7 @@ TEST(Parser, if_block_variable)
 
 TEST(Parser, if_else)
 {
-  test("kprobe:sys_open { if (pid > 10000) { $s = \"a\"; } else { $s= \"b\"; }; printf(\"%d is high\\n\", pid, $s); }",
+  test("kprobe:sys_open { if (pid > 10000) { $s = \"a\"; } else { $s= \"b\"; } printf(\"%d is high\\n\", pid, $s); }",
        "Program\n"
        " kprobe:sys_open\n"
        "  if\n"