[THRIFT-4781] C++ clients crash when exceptions are typedefed in the IDL

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 0.11.0, 0.12.0
• Component/s: C++ - Compiler
• Assignee: Unassigned
• Reporter: Andrej Nazarov
• Created: 08/Feb/19 10:57
• Updated: 08/Feb/21 08:53

Description

If exceptions are typedefed in the IDL, they're generated as pointers in Cpp. This causes a runtime crash (memory access violation) on the C++ client-side when a server sends that exception and the client tries to read it. Example follows:

service.thrift

namespace * thrifttest.service
include "errors.thrift"
typedef errors.FooError FooError
service FooBarService
{
	string getFooString(1: i32 stringLength) throws (1: FooError e);
	string getBarString(1: i32 stringLength) throws (1: errors.BarError e);
}

errors.thrift

namespace * thrifttest.errors
exception FooError {
  1: string message
}
exception BarError {
  1: string message
}

FooBarService.h

class FooBarService_getFooString_presult {
 public:
  virtual ~FooBarService_getFooString_presult() throw();
  std::string* success;
  FooError* e; //note pointer declaration of the exception field
// snip...

class FooBarService_getBarString_presult {
 public:
  virtual ~FooBarService_getBarString_presult() throw();
  std::string* success;
   ::thrifttest::errors::BarError e; //note different declaration of the exception field
//snip

FooBarService.cpp

uint32_t FooBarService_getFooString_presult::read(::apache::thrift::protocol::TProtocol* iprot) {
// snip...
  while (true)
  {
// snip...
    switch (fid)
    {
// snip...
      case 1:
        if (ftype == ::apache::thrift::protocol::T_STRUCT) {
          xfer += (*(this->e)).read(iprot); // <-- this line causes access violation crash because the pointer is not initialized
          this->__isset.e = true;
       // snip...

uint32_t FooBarService_getBarString_presult::read(::apache::thrift::protocol::TProtocol* iprot) {
// snip...
  while (true)
  {
// snip...
    switch (fid)
    {
// snip...
      case 1:
        if (ftype == ::apache::thrift::protocol::T_STRUCT) {
          xfer += this->e.read(iprot); //<-- this gets read OK.
          this->__isset.e = true;
//snip

This happens regardless of server language (reproducible if server throwing the exceptions is Java, Python or C++)
I guess this logic in t_cpp_generator.cc:1104 gets deceived in case of typedefed exceptions:

t_cpp_generator.cc

(pointers && !(*m_iter)->get_type()->is_xception()),

I'm no Thrift compiler expert, but I assume there is a reason why you don't want exceptions to be declared as pointers. Yet in this case they clearly are.