compiler: avoid GCC middle-end control warnings
GCC has started emitting "control reaches end of non-void function"
warnings. Avoid them for Go by 1) marking the builtin function panic
and the compiler-generated function __go_runtime_error as not
returning and 2) adding a default case to the switch used for select
statements that simply calls __builtin_unreachable.
Fixes golang/go#22767
Change-Id: Ic278dd841369ab922e3d791e340a3831227c2f9d
Reviewed-on: https://go-review.googlesource.com/80416
Reviewed-by: Than McIntosh <thanm@google.com>
diff --git a/go/backend.h b/go/backend.h
index 48dbe7e..601e7c9 100644
--- a/go/backend.h
+++ b/go/backend.h
@@ -711,12 +711,15 @@
// IS_INLINABLE is true if the function can be inlined.
// DISABLE_SPLIT_STACK is true if this function may not split the stack; this
// is used for the implementation of recover.
+ // DOES_NOT_RETURN is true for a function that does not return; this is used
+ // for the implementation of panic.
// IN_UNIQUE_SECTION is true if this function should be put into a unique
// location if possible; this is used for field tracking.
virtual Bfunction*
function(Btype* fntype, const std::string& name, const std::string& asm_name,
bool is_visible, bool is_declaration, bool is_inlinable,
- bool disable_split_stack, bool in_unique_section, Location) = 0;
+ bool disable_split_stack, bool does_not_return,
+ bool in_unique_section, Location) = 0;
// Create a statement that runs all deferred calls for FUNCTION. This should
// be a statement that looks like this in C++:
diff --git a/go/gogo.cc b/go/gogo.cc
index 74b4595..b1c7807 100644
--- a/go/gogo.cc
+++ b/go/gogo.cc
@@ -711,7 +711,7 @@
Bfunction* pfunc = this->backend()->function(fntype, user_name, init_name,
true, true, true, false,
- false, unknown_loc);
+ false, false, unknown_loc);
Bexpression* pfunc_code =
this->backend()->function_code_expression(pfunc, unknown_loc);
Bexpression* pfunc_call =
@@ -5435,8 +5435,8 @@
this->fndecl_ =
gogo->backend()->function(functype, no->get_id(gogo), asm_name,
is_visible, false, is_inlinable,
- disable_split_stack, in_unique_section,
- this->location());
+ disable_split_stack, false,
+ in_unique_section, this->location());
}
return this->fndecl_;
}
@@ -5448,6 +5448,8 @@
{
if (this->fndecl_ == NULL)
{
+ bool does_not_return = false;
+
// Let Go code use an asm declaration to pick up a builtin
// function.
if (!this->asm_name_.empty())
@@ -5459,6 +5461,10 @@
this->fndecl_ = builtin_decl;
return this->fndecl_;
}
+
+ if (this->asm_name_ == "runtime.gopanic"
+ || this->asm_name_ == "__go_runtime_error")
+ does_not_return = true;
}
std::string asm_name;
@@ -5475,8 +5481,8 @@
Btype* functype = this->fntype_->get_backend_fntype(gogo);
this->fndecl_ =
gogo->backend()->function(functype, no->get_id(gogo), asm_name,
- true, true, true, false, false,
- this->location());
+ true, true, true, false, does_not_return,
+ false, this->location());
}
return this->fndecl_;
diff --git a/go/runtime.def b/go/runtime.def
index 6df5349..ef148ee 100644
--- a/go/runtime.def
+++ b/go/runtime.def
@@ -363,6 +363,9 @@
DEF_GO_RUNTIME(FIELDTRACK, "__go_fieldtrack", P1(POINTER), R0())
+// Unreachable code.
+DEF_GO_RUNTIME(UNREACHABLE, "__builtin_unreachable", P0(), R0())
+
// Remove helper macros.
#undef ABFT6
#undef ABFT2
diff --git a/go/statements.cc b/go/statements.cc
index d3878a6..93718ff 100644
--- a/go/statements.cc
+++ b/go/statements.cc
@@ -4866,8 +4866,8 @@
Location location)
{
size_t count = this->clauses_.size();
- std::vector<std::vector<Bexpression*> > cases(count);
- std::vector<Bstatement*> clauses(count);
+ std::vector<std::vector<Bexpression*> > cases(count + 1);
+ std::vector<Bstatement*> clauses(count + 1);
Type* int_type = Type::lookup_integer_type("int");
@@ -4905,10 +4905,15 @@
return context->backend()->expression_statement(bfunction, bcall);
}
+ Bfunction* bfunction = context->function()->func_value()->get_decl();
+
+ Expression* crash = Runtime::make_call(Runtime::UNREACHABLE, location, 0);
+ Bexpression* bcrash = crash->get_backend(context);
+ clauses[count] = context->backend()->expression_statement(bfunction, bcrash);
+
std::vector<Bstatement*> statements;
statements.reserve(2);
- Bfunction* bfunction = context->function()->func_value()->get_decl();
Bstatement* switch_stmt = context->backend()->switch_statement(bfunction,
bcall,
cases,
