Alberto Barbaro via llvm-dev
2019-Jan-22 19:20 UTC
[llvm-dev] How to get the value of an i8*?
Hi all, sorry to ask again but this problem is killing me :) So I have the following C code: #include<stdio.h> int main(int argc, char *argv[]) { printf("%s\n", argv[0]); return argc; } That is translated into ; ModuleID = 'argv.bc' source_filename = "argv.c" target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128" target triple = "x86_64-pc-linux-gnu" @.str = private unnamed_addr constant [4 x i8] c"%s\0A\00", align 1 ; Function Attrs: noinline nounwind optnone uwtable define i32 @main(i32, i8**) #0 { %3 = alloca i32, align 4 %4 = alloca i32, align 4 %5 = alloca i8**, align 8 store i32 0, i32* %3, align 4 store i32 %0, i32* %4, align 4 store i8** %1, i8*** %5, align 8 %6 = load i8**, i8*** %5, align 8 %7 = getelementptr inbounds i8*, i8** %6, i64 0 %8 = load i8*, i8** %7, align 8 %9 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str, i32 0, i32 0), i8* %8) %10 = load i32, i32* %4, align 4 ret i32 %10 } declare i32 @printf(i8*, ...) #1 attributes #0 = { noinline nounwind optnone uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" } attributes #1 = { "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "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" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" } !llvm.module.flags = !{!0} !llvm.ident = !{!1} !0 = !{i32 1, !"wchar_size", i32 4} !1 = !{!"clang version 6.0.1-svn334776-1~exp1~20181018152737.116 (branches/release_60)"} I'm still experimenting with the Interpreter class... I know that %8 holds the pointer to argv[0] and I would like to extract the value. I though the right approach would have been to do what it is done inside visitLoadInst: ExecutionContext &SF = ECStack.back(); GenericValue SRC = getOperandValue(I.getPointerOperand(), SF); GenericValue *Ptr = (GenericValue*)GVTOP(SRC); GenericValue Result; LoadValueFromMemory(Result, Ptr, I.getType()); Instead of I.getType() I used getInt32Ty(context) and instead of Ptr I used the result returned by first LoadValueFromMemory. After that I print "newResult.Int" but I always have 0 as a result. I cannot understand why. Can someone help me to have argv[0] taken from the memory? Thanks a lot -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20190122/fb11e973/attachment.html>