How to view Clang AST?

Question

I am trying to get hold on Clang. So, I would like to view the AST generated by Clang after parsing the given program. Is it possible to dump AST in .dot or .viz format? Is there any tool out there?

score 68 · Answer 1 · answered Sep 16 '17 at 17:46

68

The method with -cc1 invocation will have problem with includes and recognizing C++.

For full-featured parsing, use:

clang -Xclang -ast-dump file.cpp

answered Sep 16 '17 at 17:46

Kornel

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Ah, this is the switch I always forget. This prints the AST with pretty colours in Windows ^^ – Cameron Oct 18 '17 at 13:43

score 59 · Accepted Answer · edited May 17 '15 at 14:54

59

Clang supports showing the AST with Graphviz's dotty -- you can grab the temporary .dot file generated (name is printed out) to get the graph source.

clang -cc1 -ast-view your_file.c

You can also print to the command line with:

clang -cc1 -ast-dump your_file.c

or:

clang -cc1 -ast-print your_file.c

or in 3.3:

clang -cc1 -ast-dump-xml your_file.c

but this was removed later as pointed by Lukas Kubanek in the comment.

edited May 17 '15 at 14:54

Ciro Santilli OurBigBook.com

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answered Sep 03 '13 at 10:17

cpt. jazz

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The XML printer is no longer supported. See http://llvm.org/viewvc/llvm-project?view=revision&revision=127141 – Lukáš Kubánek Apr 23 '14 at 19:40
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`-ast-view` also seems to require compile time support, which is not on by default on Ubuntu 14.04 :-( `-ast-dump` works beautifully. What is `-ast-print` supposed to do? It just prints the code itself with some empty lines afterwards. – Ciro Santilli OurBigBook.com May 17 '15 at 14:49
According to the revision comment the xml printer never actually worked properly. – wheredidthatnamecomefrom May 06 '18 at 00:30
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In recent clang you can also use `-ast-dump=json`, very useful! You can add this to your answer, if you don't mind. – Arty Apr 26 '21 at 16:13

score 6 · Answer 3 · answered Aug 26 '19 at 12:24

6

For viewing the AST

clang-check -ast-dump filename.c

For to view the specific functions in a program

clang-check -ast-dump -ast-dump-filter=function_name filename.c

answered Aug 26 '19 at 12:24

Jon marsh

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score 3 · Answer 4 · answered Sep 17 '19 at 20:07

3

I am using following:

clang my_file.h -I. -Xclang -ast-dump -fsyntax-only -fno-color-diagnostics -Wno-visibility

IMHO This is more suitable for machine parsing.

answered Sep 17 '19 at 20:07

shapkin

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When I run this on a single file from a library I get errors about missing header files, even with the `-fsyntax-only` flag. Any ideas? – Taylor Evanson Aug 22 '22 at 14:26
@TaylorEvanson Same problem – Veno Feb 17 '23 at 06:57

How to view Clang AST?

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