[cfe-users] Fwd: Re: [llvm-dev] Overriding macro values defined in source code

[Sudhindra kulkarni via cfe-users]

Thanks Richard for the answer.

I have another question regarding the include(-I) option.

If we have a c file called cfile.c and a header file called header.h both
in the same directory say (dir x).  cfile.c includes header.h as shown below
#include "header.h"
And if in some other directory say (dir y)we have another header file with
the same name(header.h) but with a different content then when I try to
generate the preprocessed file using the below command,
clang.exe -E path of cfile.c -I path of dir y
The header.h present in the directory dir x is getting considered even
though -I points to dir y.

Is this the intended behavior that the current directory is searched first
for the header files irrespective of the directory provided against the -I
option.
If not how to make clang consider only the directories provided against the
-I option and not the current directory.

Thanks in advance







On May 9, 2019 5:01 AM, "Richard Smith" <richard at metafoo.co.uk> wrote:

On Mon, 6 May 2019 at 23:09, Sudhindra kulkarni via cfe-users
<cfe-users at lists.llvm.org> wrote:
>
>
> ---------- Forwarded message ----------
> From: "Tim Northover" <t.p.northover at gmail.com>
> Date: May 1, 2019 3:48 PM
> Subject: Re: [llvm-dev] Overriding macro values defined in source code
> To: "Sudhindra kulkarni" <sudhindrakkulkarni102 at gmail.com>
> Cc: "LLVM Developers Mailing List" <llvm-dev at lists.llvm.org>
>
> On Tue, 30 Apr 2019 at 22:28, Sudhindra kulkarni via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
> > Is it possible to override the value of AVAL through the -D option?
> > For eg is it possible to set the value of AVAL to 2 through -D in clang
?
>
> This is more a question for the cfe-users list, but as far as I know
> there's no way to prevent redefinitions in source files.
>
> Cheers.
>
> Tim.
>
> Hi Team,
>                  Consider the below C code,
> #define AVAL 5
> void func()
> {
> int a=5;
> if(a==AVAL)
> {
> //Do something
> }
> else
> {
> //Do something else
> }
>
> }
> My question is
> Is it possible to override the value of AVAL through the -D option?
> For eg is it possible to set the value of AVAL to 2 through -D in clang
so that the else part executes?
> Also apart from -D option we are also open to other ways of achieving this

The normal approach is to change the source to something like

#ifndef AVAL
#define AVAL 5
#endif

> Thanks in advance
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> cfe-users mailing list
> cfe-users at lists.llvm.org
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