问题
I'm trying to get exceptions working with llvm for a very simple example, that I can later build on but i'm running into some real difficulties and i'm not sure why.
I got clang to give me the following llir code, that I am passing into the MCJIT
; llvm-as c++exn.ll && llvm-ld -native c++exn.bc -lstdc++.6 && ./a.out
%"class.std::ios_base::Init" = type { i8 }
%"class.std::basic_ostream" = type { i32 (...)**, %"class.std::basic_ios" }
%"class.std::basic_ios" = type { %"class.std::ios_base", %"class.std::basic_ostream"*, i8, i8, %"class.std::basic_streambuf"*, %"class.std::ctype"*, %"class.std::num_put"*, %"class.std::num_get"* }
%"class.std::ios_base" = type { i32 (...)**, i64, i64, i32, i32, i32, %"struct.std::ios_base::_Callback_list"*, %"struct.std::ios_base::_Words", [8 x %"struct.std::ios_base::_Words"], i32, %"struct.std::ios_base::_Words"*, %"class.std::locale" }
%"struct.std::ios_base::_Callback_list" = type { %"struct.std::ios_base::_Callback_list"*, void (i32, %"class.std::ios_base"*, i32)*, i32, i32 }
%"struct.std::ios_base::_Words" = type <{ i8*, i32, [4 x i8] }>
%"class.std::locale" = type { %"class.std::locale::_Impl"* }
%"class.std::locale::_Impl" = type { i32, %"class.std::locale::facet"**, i64, %"class.std::locale::facet"**, i8** }
%"class.std::locale::facet" = type <{ i32 (...)**, i32, [4 x i8] }>
%"class.std::basic_streambuf" = type { i32 (...)**, i8*, i8*, i8*, i8*, i8*, i8*, %"class.std::locale" }
%"class.std::ctype" = type <{ %"class.std::locale::facet.base", [4 x i8], i32*, i8, [7 x i8], i32*, i32*, i16*, i8, [256 x i8], [256 x i8], i8, [6 x i8] }>
%"class.std::locale::facet.base" = type <{ i32 (...)**, i32 }>
%"class.std::num_put" = type { %"class.std::locale::facet.base", [4 x i8] }
%"class.std::num_get" = type { %"class.std::locale::facet.base", [4 x i8] }
%class.new_exception = type { %"class.std::exception" }
%"class.std::exception" = type { i32 (...)** }
$_ZN13new_exceptionC2Ev = comdat any
$_ZN13new_exceptionD2Ev = comdat any
$__clang_call_terminate = comdat any
$_ZNSt9exceptionC2Ev = comdat any
$_ZN13new_exceptionD0Ev = comdat any
$_ZTS13new_exception = comdat any
$_ZTI13new_exception = comdat any
$_ZTV13new_exception = comdat any
@_ZStL8__ioinit = internal global %"class.std::ios_base::Init" zeroinitializer, align 1
@_ZTVN10__cxxabiv120__si_class_type_infoE = external global i8*
@_ZTS13new_exception = linkonce_odr constant [16 x i8] c"13new_exception\00", comdat
@_ZTISt9exception = external constant i8*
@_ZTI13new_exception = linkonce_odr constant { i8*, i8*, i8* } { i8* bitcast (i8** getelementptr inbounds (i8*, i8** @_ZTVN10__cxxabiv120__si_class_type_infoE, i64 2) to i8*), i8* getelementptr inbounds ([16 x i8], [16 x i8]* @_ZTS13new_exception, i32 0, i32 0), i8* bitcast (i8** @_ZTISt9exception to i8*) }, comdat
@_ZSt4cout = external global %"class.std::basic_ostream", align 8
@.str = private unnamed_addr constant [11 x i8] c"caught !!!\00", align 1
@_ZTV13new_exception = linkonce_odr unnamed_addr constant [5 x i8*] [i8* null, i8* bitcast ({ i8*, i8*, i8* }* @_ZTI13new_exception to i8*), i8* bitcast (void (%class.new_exception*)* @_ZN13new_exceptionD2Ev to i8*), i8* bitcast (void (%class.new_exception*)* @_ZN13new_exceptionD0Ev to i8*), i8* bitcast (i8* (%"class.std::exception"*)* @_ZNKSt9exception4whatEv to i8*)], comdat, align 8
@_ZTVSt9exception = external unnamed_addr constant [5 x i8*]
@llvm.global_ctors = appending global [1 x { i32, void ()*, i8* }] [{ i32, void ()*, i8* } { i32 65535, void ()* @_GLOBAL__sub_I_runtime_gen.cpp, i8* null }]
; Function Attrs: uwtable
define internal void @__cxx_global_var_init() #0 {
call void @_ZNSt8ios_base4InitC1Ev(%"class.std::ios_base::Init"* @_ZStL8__ioinit)
%1 = call i32 @atexit(void ()* @__dtor__ZStL8__ioinit) #2
ret void
}
declare void @_ZNSt8ios_base4InitC1Ev(%"class.std::ios_base::Init"*) #1
declare void @_ZNSt8ios_base4InitD1Ev(%"class.std::ios_base::Init"*) #1
; Function Attrs: uwtable
define internal void @__dtor__ZStL8__ioinit() #0 {
call void @_ZNSt8ios_base4InitD1Ev(%"class.std::ios_base::Init"* @_ZStL8__ioinit)
ret void
}
; Function Attrs: nounwind
declare i32 @atexit(void ()*) #2
; Function Attrs: uwtable
define void @_Z5functv() #0 {
%1 = call i8* @__cxa_allocate_exception(i64 8) #2
%2 = bitcast i8* %1 to %class.new_exception*
%3 = bitcast %class.new_exception* %2 to i8*
call void @llvm.memset.p0i8.i64(i8* %3, i8 0, i64 8, i32 16, i1 false)
call void @_ZN13new_exceptionC2Ev(%class.new_exception* %2) #2
call void @__cxa_throw(i8* %1, i8* bitcast ({ i8*, i8*, i8* }* @_ZTI13new_exception to i8*), i8* bitcast (void (%class.new_exception*)* @_ZN13new_exceptionD2Ev to i8*)) #11
unreachable
; No predecessors!
ret void
}
declare i8* @__cxa_allocate_exception(i64)
; Function Attrs: argmemonly nounwind
declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1) #3
; Function Attrs: inlinehint nounwind uwtable
define linkonce_odr void @_ZN13new_exceptionC2Ev(%class.new_exception* %this) unnamed_addr #4 comdat align 2 {
%1 = alloca %class.new_exception*, align 8
store %class.new_exception* %this, %class.new_exception** %1, align 8
%2 = load %class.new_exception*, %class.new_exception** %1, align 8
%3 = bitcast %class.new_exception* %2 to %"class.std::exception"*
call void @_ZNSt9exceptionC2Ev(%"class.std::exception"* %3) #2
%4 = bitcast %class.new_exception* %2 to i32 (...)***
store i32 (...)** bitcast (i8** getelementptr inbounds ([5 x i8*], [5 x i8*]* @_ZTV13new_exception, i64 0, i64 2) to i32 (...)**), i32 (...)*** %4, align 8
ret void
}
; Function Attrs: inlinehint nounwind uwtable
define linkonce_odr void @_ZN13new_exceptionD2Ev(%class.new_exception* %this) unnamed_addr #4 comdat align 2 {
%1 = alloca %class.new_exception*, align 8
store %class.new_exception* %this, %class.new_exception** %1, align 8
%2 = load %class.new_exception*, %class.new_exception** %1, align 8
%3 = bitcast %class.new_exception* %2 to %"class.std::exception"*
call void @_ZNSt9exceptionD2Ev(%"class.std::exception"* %3) #2
ret void
}
declare void @__cxa_throw(i8*, i8*, i8*)
; Function Attrs: uwtable
define void @_Z4ctchv() #0 personality i8* bitcast (i32 (...)* @__gxx_personality_seh0 to i8*) {
%1 = alloca i8*
%2 = alloca i32
%o = alloca %class.new_exception*, align 8
invoke void @_Z5functv()
to label %3 unwind label %4
; <label>:3 ; preds = %0
br label %20
; <label>:4 ; preds = %0
%5 = landingpad { i8*, i32 }
catch i8* bitcast ({ i8*, i8*, i8* }* @_ZTI13new_exception to i8*)
%6 = extractvalue { i8*, i32 } %5, 0
store i8* %6, i8** %1, align 8
%7 = extractvalue { i8*, i32 } %5, 1
store i32 %7, i32* %2, align 4
br label %8
; <label>:8 ; preds = %4
%9 = load i32, i32* %2, align 4
%10 = call i32 @llvm.eh.typeid.for(i8* bitcast ({ i8*, i8*, i8* }* @_ZTI13new_exception to i8*)) #2
%11 = icmp eq i32 %9, %10
br i1 %11, label %12, label %26
; <label>:12 ; preds = %8
%13 = load i8*, i8** %1, align 8
%14 = call i8* @__cxa_begin_catch(i8* %13) #2
%15 = bitcast i8* %14 to %class.new_exception*
store %class.new_exception* %15, %class.new_exception** %o, align 8
%16 = invoke dereferenceable(272) %"class.std::basic_ostream"* @_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc(%"class.std::basic_ostream"* dereferenceable(272) @_ZSt4cout, i8* getelementptr inbounds ([11 x i8], [11 x i8]* @.str, i32 0, i32 0))
to label %17 unwind label %21
; <label>:17 ; preds = %12
%18 = invoke dereferenceable(272) %"class.std::basic_ostream"* @_ZNSolsEPFRSoS_E(%"class.std::basic_ostream"* %16, %"class.std::basic_ostream"* (%"class.std::basic_ostream"*)* @_ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_)
to label %19 unwind label %21
; <label>:19 ; preds = %17
call void @__cxa_end_catch()
br label %20
; <label>:20 ; preds = %19, %3
ret void
; <label>:21 ; preds = %17, %12
%22 = landingpad { i8*, i32 }
cleanup
%23 = extractvalue { i8*, i32 } %22, 0
store i8* %23, i8** %1, align 8
%24 = extractvalue { i8*, i32 } %22, 1
store i32 %24, i32* %2, align 4
invoke void @__cxa_end_catch()
to label %25 unwind label %31
; <label>:25 ; preds = %21
br label %26
; <label>:26 ; preds = %25, %8
%27 = load i8*, i8** %1, align 8
%28 = load i32, i32* %2, align 4
%29 = insertvalue { i8*, i32 } undef, i8* %27, 0
%30 = insertvalue { i8*, i32 } %29, i32 %28, 1
resume { i8*, i32 } %30
; <label>:31 ; preds = %21
%32 = landingpad { i8*, i32 }
catch i8* null
%33 = extractvalue { i8*, i32 } %32, 0
call void @__clang_call_terminate(i8* %33) #12
unreachable
}
declare i32 @__gxx_personality_seh0(...)
; Function Attrs: nounwind readnone
declare i32 @llvm.eh.typeid.for(i8*) #5
declare i8* @__cxa_begin_catch(i8*)
declare dereferenceable(272) %"class.std::basic_ostream"* @_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc(%"class.std::basic_ostream"* dereferenceable(272), i8*) #1
declare dereferenceable(272) %"class.std::basic_ostream"* @_ZNSolsEPFRSoS_E(%"class.std::basic_ostream"*, %"class.std::basic_ostream"* (%"class.std::basic_ostream"*)*) #1
declare dereferenceable(272) %"class.std::basic_ostream"* @_ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_(%"class.std::basic_ostream"* dereferenceable(272)) #1
declare void @__cxa_end_catch()
; Function Attrs: noinline noreturn nounwind
define linkonce_odr hidden void @__clang_call_terminate(i8*) #6 comdat {
%2 = call i8* @__cxa_begin_catch(i8* %0) #2
call void @_ZSt9terminatev() #12
unreachable
}
declare void @_ZSt9terminatev()
; Function Attrs: norecurse uwtable
define i32 @main() #7 {
call void @_Z4ctchv()
ret i32 0
}
; Function Attrs: nounwind uwtable
define linkonce_odr void @_ZNSt9exceptionC2Ev(%"class.std::exception"* %this) unnamed_addr #8 comdat align 2 {
%1 = alloca %"class.std::exception"*, align 8
store %"class.std::exception"* %this, %"class.std::exception"** %1, align 8
%2 = load %"class.std::exception"*, %"class.std::exception"** %1, align 8
%3 = bitcast %"class.std::exception"* %2 to i32 (...)***
store i32 (...)** bitcast (i8** getelementptr inbounds ([5 x i8*], [5 x i8*]* @_ZTVSt9exception, i64 0, i64 2) to i32 (...)**), i32 (...)*** %3, align 8
ret void
}
; Function Attrs: inlinehint nounwind uwtable
define linkonce_odr void @_ZN13new_exceptionD0Ev(%class.new_exception* %this) unnamed_addr #4 comdat align 2 {
%1 = alloca %class.new_exception*, align 8
store %class.new_exception* %this, %class.new_exception** %1, align 8
%2 = load %class.new_exception*, %class.new_exception** %1, align 8
call void @_ZN13new_exceptionD2Ev(%class.new_exception* %2) #2
%3 = bitcast %class.new_exception* %2 to i8*
call void @_ZdlPv(i8* %3) #13
ret void
}
; Function Attrs: nounwind
declare i8* @_ZNKSt9exception4whatEv(%"class.std::exception"*) #9
; Function Attrs: nobuiltin nounwind
declare void @_ZdlPv(i8*) #10
; Function Attrs: nounwind
declare void @_ZNSt9exceptionD2Ev(%"class.std::exception"*) #9
; Function Attrs: uwtable
define internal void @_GLOBAL__sub_I_runtime_gen.cpp() #0 {
call void @__cxx_global_var_init()
ret void
}
attributes #0 = { uwtable "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #1 = { "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #2 = { nounwind }
attributes #3 = { argmemonly nounwind }
attributes #4 = { inlinehint nounwind uwtable "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #5 = { nounwind readnone }
attributes #6 = { noinline noreturn nounwind }
attributes #7 = { norecurse uwtable "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #8 = { nounwind uwtable "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #9 = { nounwind "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #10 = { nobuiltin nounwind "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #11 = { noreturn }
attributes #12 = { noreturn nounwind }
attributes #13 = { builtin nounwind }
This is the llir code generated from the following C++ code.
#include <iostream>
#include <exception>
using namespace std;
class new_exception : public exception {
const char* what() {
return "new_exception";
}
};
void funct() {
throw new_exception();
}
void ctch() {
try {
funct();
} catch(new_exception& o) {
std::cout << "caught !!!" << std::endl;
}
}
int main() {
ctch();
}
When loaded it compiled by MCJIT on windows without issue but when run it crashes, when run with gdb it halts with message 'RaiseException() ?:Unknown signal'.
As far as I am aware the exception is being handled correctly, "caught" by the code and so shouldn't be the issue.
Is my use of the personality function correct, I have looked through answers that suggest the use of SEH based personality on windows might be wrong. What is the alternative if this is wrong and why would clang write incorrect code?
Platform is Windows X86_64
target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-w64-windows-gnu"
回答1:
I'm starting to use exceptions in C++ for Windows with clang and msvc 2015, and they do work very well with standard C++ exceptions (that Microsoft documentation calls synchronous) -- no need to use SEH (AKA Structured Exception Handling), that Microsoft calls asynchronous.
回答2:
Your Code contain an error. The main method doesn't return an int, please check it:
Change this
int main() {
ctch();
}
By this:
int main() {
ctch();
return 0;
}
来源：https://stackoverflow.com/questions/41304787/llvm-exceptions-raiseexception-unknown-signal