Fix crash when using $0

bpftrace · Jul 9, 2019 · b41d66d · b41d66d
1 parent e98530c
commit b41d66d
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Showing 2 changed files with 8 additions and 0 deletions.
diff --git a/src/ast/semantic_analyser.cpp b/src/ast/semantic_analyser.cpp
@@ -22,6 +22,10 @@ void SemanticAnalyser::visit(Integer &integer)
 
 void SemanticAnalyser::visit(PositionalParameter &param)
 {
+  if (param.n <= 0) {
+    err_ << "$" << param.n << " is not a valid parameter" << std::endl;
+  }
+
   param.type = SizedType(Type::integer, 8);
   if (is_final_pass()) {
     std::string pstr = bpftrace_.get_param(param.n, param.is_in_str);

diff --git a/tests/semantic_analyser.cpp b/tests/semantic_analyser.cpp
@@ -930,12 +930,16 @@ TEST(semantic_analyser, positional_parameters)
   bpftrace.add_param("123");
   bpftrace.add_param("hello");
 
+  test(bpftrace, "kprobe:f { printf(\"%d\", $0); }", 1);
+  test(bpftrace, "kprobe:f { printf(\"%s\", str($0)); }", 1);
+
   test(bpftrace, "kprobe:f { printf(\"%d\", $1); }", 0);
   test(bpftrace, "kprobe:f { printf(\"%s\", str($1)); }", 10);
 
   test(bpftrace, "kprobe:f { printf(\"%s\", str($2)); }", 0);
   test(bpftrace, "kprobe:f { printf(\"%d\", $2); }", 10);
 
+  // Parameters are not required to exist to be used:
   test(bpftrace, "kprobe:f { printf(\"%s\", str($3)); }", 0);
   test(bpftrace, "kprobe:f { printf(\"%d\", $3); }", 0);
 }