YAML IO crashes in Input::beginMapping() when trying to read from an empty string

[llvmbot]

Bugzilla Link	15927
Resolution	FIXED
Resolved on	Nov 18, 2013 09:51
Version	trunk
OS	Linux
Reporter	LLVM Bugzilla Contributor
CC	@eugenis,@kcc

Extended Description

The code to reproduce this is:
#include "llvm/Support/YAMLTraits.h"
struct T { int a; };

namespace llvm {
namespace yaml {
template <> struct MappingTraits {
static void mapping(llvm::yaml::IO &IO, T &T) {
IO.mapOptional("a", T.a);
}
};
}
}

int main(int argc, const char **argv) {
llvm::yaml::Input Input("");
T T;
Input >> T;
return 0;
}

---

$ ./test
test: llvm/include/llvm/Support/Casting.h:97: static bool llvm::isa_impl_cl<llvm::yaml::Input::MapHNode, const llvm::yaml::Input::HNode *>::doit(const From *) [To = llvm::yaml::Input::MapHNode, From = const llvm::yaml::Input::HNode *]: Assertion `Val && "isa<> used on a null pointer"' failed.
Aborted (core dumped)

The problem is in the line 88 of lib/Support/YAMLTraits.cpp:
88 MapHNode *MN = dyn_cast(CurrentNode);

[kcc]

I observe the same assertion when compiling a simple .c test with msan:

typedef char int8_t;
int8_t a;
b;
c;
int8_t
fn1 (p1) {
return a < 0 || p1 || 0 > 1 >> p1 ? a : a << p1;
}
fn2 () {
int8_t d;
c = fn1 (b << 13);
d = c < 0 ? : 0;
fn3 (d);
}

% clang -c -O3 -g -fsanitize=memory j.c

llvm/include/llvm/Support/Casting.h:97: static bool llvm::isa_impl_cl<llvm::ConstantSDNode, const llvm::SDNode *>::doit(const From *) [To = llvm::ConstantSDNode, From = const llvm::SDNode *]: Assertion `Val && "isa<> used on a null pointer"' failed.
11 clang-3.3 0x0000000000b62eed llvm::SelectionDAG::Combine(llvm::CombineLevel, llvm::AliasAnalysis&, llvm::CodeGenOpt::Level) + 733
12 clang-3.3 0x0000000000c1f3a7 llvm::SelectionDAGISel::CodeGenAndEmitDAG() + 871
13 clang-3.3 0x0000000000c1e7d9 llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&) + 6265
14 clang-3.3 0x0000000000c1c2a6 llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&) + 1302
15 clang-3.3 0x0000000000d6d30d llvm::MachineFunctionPass::runOnFunction(llvm::Function&) + 125

[llvmbot]

I observe the same assertion when compiling a simple .c test with msan:
This means there's another wrong usage of isa<> function, but this is an absolutely unrelated issue.

[llvmbot]

Fixed in r195016.