https://llvm.org/bugs/show_bug.cgi?id=23491
Bug ID: 23491
Summary: clang doesn't follow the SysV i386 ABI for global
functions returning structures.
Product: clang
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: libclang
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected]
Classification: Unclassified
Created attachment 14314
--> https://llvm.org/bugs/attachment.cgi?id=14314&action=edit
main file which calls foo1().
According to SysV i386 ABI document "SYSTEM V APPLICATION BINARY INTERFACE,
Intel386 Architecture Processor Supplement, Fourth Edition":
A function returning structure sets %eax to the value of the original address
of the structure while returning so that when the caller receives control
again, the address of the returned object resides in register %eax and can be
used to access the object.
Compiling sup.c (contents given below) using clang 3.7.0, the generated
assembly does not update %eax with the address of the structure while returning
from the function foo1()
File sup.c contains a function foo1() that accepts a structure as an argument
and returns the same structure. The contents of the file are:
struct baar{
int a;
int b;
};
struct baar foo1(struct baar x)
{
return x ;
}
Compilation command used:
clang -g -O0 -m32 -c sup.c -o sup.o
Attached here is main.c file from which a call to foo1() is made.
main.o and sup.o files were linked to generate executable.
Platform: Ubuntu 14.04, x86_64 GNU/Linux
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