http://llvm.org/bugs/show_bug.cgi?id=10058
Summary: C standard incompatibility concerning untyped
functions (and varargs)
Product: clang
Version: 2.8
Platform: PC
OS/Version: Linux
Status: NEW
Severity: normal
Priority: P
Component: LLVM Codegen
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected]
Created an attachment (id=6668)
--> (http://llvm.org/bugs/attachment.cgi?id=6668)
The C source file.
Pre-standard function definitions (with untyped parameters - e.g. "foo(a,b)
{...}") are processed in a wrong and inconsistent way.
Translate the attached C file with the following command:
clang example.c -emit-llvm -S
When you look at the resulting ll file (in the second attachment), you will see
that the definitions of the functions f1-f6 are all right and as expected
(everything defaults to integer). However, they are used (in the function main)
as if they were variadic. This behaviour is in contradiction with C standard
(functions are variadic only if explicitly declared and/or defined as such).
This (probably) happens during the LLVM IR generation (hence the component
"LLVM Codegen" was set instead of "Frontend").
Note: I understand that this is probably a "feature".
Also, it is easy for a backend to deal with this. However, let's say that you
are using clang for something else (let's say, semantics extraction) and you
need a correct result.
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