[llvm-dev] How to call C function 'malloc' ?

[AllenShow via llvm-dev]

> On Dec 6, 2015, at 10:20 AM, AllenShow <xiulunlin at gmail.com> wrote:
> 
> Thanks for you answer.
> Actually I have tried like this, however, I want to know how could I implement this Just-in-time with ExecutionEngineer.
> I have no idea how to make EE recognise libgcc.dylib.
>> On Dec 6, 2015, at 5:25 AM, Bruce Hoult <bruce at hoult.org <mailto:bruce at hoult.org>> wrote:
>> 
>> The answer to such questions is usually best obtained by looking at what clang does. See below.
>> 
>> $ cat foo.c
>> #include <stdlib.h>
>> void* foo(int i){return malloc(i);}
>> $ clang -emit-llvm -S foo.c
>> $ cat foo.ll
>> ; ModuleID = 'foo.c'
>> target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
>> target triple = "x86_64-apple-macosx10.10.0"
>> 
>> ; Function Attrs: nounwind ssp uwtable
>> define i8* @foo(i32 %i) #0 {
>>   %1 = alloca i32, align 4
>>   store i32 %i, i32* %1, align 4
>>   %2 = load i32* %1, align 4
>>   %3 = sext i32 %2 to i64
>>   %4 = call i8* @malloc(i64 %3)
>>   ret i8* %4
>> }
>> 
>> declare i8* @malloc(i64) #1
>> 
>> attributes #0 = { nounwind ssp uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
>> attributes #1 = { "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
>> 
>> !llvm.ident = !{!0}
>> 
>> !0 = metadata !{metadata !"Apple LLVM version 6.0 (clang-600.0.56) (based on LLVM 3.5svn)"}
>> 
>> 
>> 
>> On Thu, Dec 3, 2015 at 4:03 PM, AllenShow via llvm-dev <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
>> Hi, everyone.
>> I am new to llvm and I want to use C function “malloc" and “free" to do heap allocation, but It seems it is not a built-in function like ‘’printf” so I got an error “Unknown extern function”.
>> I use ExecutionEngineer to run my main function and how should I do to make EE link the C library I want.
>> Thanks.
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>> 
> 

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