[llvm-dev] Function start address

Muhui Jiang via llvm-dev llvm-dev at lists.llvm.org
Fri Jun 1 22:34:12 PDT 2018


Actually, No particular reason. I just think this might be a solution, then
I use think kind of method. Querying the symbol table would be a good
choice, but I prefer to use LLVM and dwarf information. I am sorry that I
am not familiar with debug_info. But thanks to your suggestions. I would
like to try to solve it with debug_info. It seems work according to your

By the way, I am still curious about the reason, why dwarf line mapping
table would lost so many function's start addresses' information. It would
be great if you have any comments on this problem. Many Thanks


2018-06-01 23:00 GMT+08:00 David Blaikie <dblaikie at gmail.com>:

> Any particular reason you're using debug info to achieve this (& if you
> are, why you're using the line table?)? You could query the
> object/executable file's symbol table to find all the functions in an
> object or executable, and the instruction/address they start at. Or, if you
> are using debug info for some reason, you could look in the debug_info
> rather than the line table, and find the DW_TAG_subprogram for each
> function and look at its low_pc.
> On Fri, Jun 1, 2018 at 3:36 AM Muhui Jiang via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>> Hi
>> I am using LLVM Pass combined with dwarf debug information to get all the
>> function's start address. My steps are below:
>> First, I write the function pass to get the start line of each function,
>> which is finished.
>> Then, based on the start line of every single function, I try to query
>> the specific line from the dwarf's line binary table, which is generated
>> with llvm-dwarfdump -debug-line.
>> However, About one third of the whole functions' start line is not found
>> in the mapping table. Thus, I can not get the start binary address. I know
>> that the mapping between source locations and binary addresses is not
>> bijective. I am using O1 optimization option. I know that some of the
>> information might be lost legitimately because of optimization. But I don't
>> think dwarf will miss so many functions' start addresses. Am I right? Any
>> useful comments and suggestions are welcomed. Many Thanks
>> Regards
>> Muhui
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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