<div dir="ltr"><div dir="ltr">On Fri, 4 Oct 2019 at 07:18, Hubert Tong via cfe-dev <<a href="mailto:cfe-dev@lists.llvm.org">cfe-dev@lists.llvm.org</a>> wrote:<br></div><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Oct 4, 2019 at 6:12 AM Gábor Márton via cfe-dev <<a href="mailto:cfe-dev@lists.llvm.org" target="_blank">cfe-dev@lists.llvm.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">I've found that the GCC __attribute__((noreturn)) is part of the type, and not parsed into a separate AST node like the C++11 [[noreturn]] or the GNU __attribute__((analyzer_noreturn)).<div>To query the GCC __attribute__((noreturn)) we can use FunctionType::getNoReturnAttr().</div><div><br></div><div>Why do we have these differences, with these attributes, why was the GCC noreturn uplifted into the Type?</div></div></blockquote><div>Because it applies to function types:</div><div>typedef void (*fptype)(void) __attribute__((__noreturn__));<br>int f(int x, fptype fp) {<br> if (x) return 42;<br> fp();<br>}</div></div></div></blockquote><div><br></div><div>Yes. We are missing the AttributedType node in the AST in this case, though:</div><div><br></div><div>typedef void (*fptype)(void) __attribute__((__noreturn__));<br>#pragma clang __debug dump fptype;<br></div><div><br></div><div>gives:</div><div><br></div><div>TypedefDecl 0x55822b34e048 <<source>:1:1, col:28> col:16 fptype 'void (*)() __attribute__((noreturn))'<br>`-PointerType 0x55822b34dff0 'void (*)() __attribute__((noreturn))'<br> `-ParenType 0x55822b34df90 'void () __attribute__((noreturn))' sugar<br> `-FunctionProtoType 0x55822b34df60 'void () __attribute__((noreturn))' noreturn cdecl<br> `-BuiltinType 0x55822b30b7e0 'void'<br><br></div><div>Consider for comparison</div><div><br></div><div>typedef int *__attribute__((address_space(3))) *p;<br>#pragma clang __debug dump p;<br></div><div><br></div><div>which gives:</div><div><br></div><div>TypedefDecl 0x5619f0bc2f90 <<source>:1:1, col:49> col:49 p 'int *__attribute__((address_space(3))) *'<br>`-PointerType 0x5619f0bc2f40 'int *__attribute__((address_space(3))) *'<br> `-AttributedType 0x5619f0bc2ee0 'int *__attribute__((address_space(3)))' sugar<br> |-PointerType 0x5619f0bc2e70 'int *'<br> | `-BuiltinType 0x5619f0b80880 'int'<br> `-QualType 0x5619f0bc2ec8 'int *__attribute__((address_space(3)))' __attribute__((address_space(3)))<br> `-PointerType 0x5619f0bc2e70 'int *'<br> `-BuiltinType 0x5619f0b80880 'int'<br><br></div><div>(The reason for this is that support for noreturn long predates AttributedType and we forgot to update the relevant code to produce the AttributedType wrapper.)</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div><br></div><div>Thanks,</div><div>Gabor</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Oct 4, 2019 at 11:40 AM Gábor Márton <<a href="mailto:martongabesz@gmail.com" target="_blank">martongabesz@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">Hi,<br><div><br></div><div>Having a source file (/tmp/attr.cpp)</div><div> void f() __attribute__((analyzer_noreturn));<br> void g() __attribute__((noreturn));<br> [[gnu::noreturn]] void h(void);<br></div><div>Generates the following AST, when clang -cc1 -ast-dump /tmp/attr.cpp is used</div><div> |-FunctionDecl 0x18a5178 </tmp/attr.cpp:1:1, col:43> col:6 f 'void ()'<br> | `-AnalyzerNoReturnAttr 0x18a5218 <col:25><br> |-FunctionDecl 0x18a5308 <line:2:1, col:34> col:6 g 'void () __attribute__((noreturn))'<br> `-FunctionDecl 0x18a5440 <line:3:19, col:30> col:24 h 'void () __attribute__((noreturn))'<br></div><div><br></div><div>I.e. the NoReturnAttr node is missing. This is very confusing, when compared to the AnalyzerNoReturnAttr, which is there.</div><div>The only difference in Attr.td is that noreturn has GCC spelling, while analyzer_noreturn has GNU spelling.</div><div>What am I missing to have a NoReturnAttr node? Do I have to specify a special extra flag for CC1 to enable GCC attributes?</div><div><br></div><div>Thanks,</div><div>Gabor</div></div>
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