Header with only macro definitions are silently processed without leaving a trace in the final preprocessed output.

[smwikipedia]

I tried with 4 files as below:

Folder structure:

C:\MISC\PCPP.TEST
    a.c
    h1.h
    h2.h
    h3.h

(a.c)

#include "h1.h"
#include "h2.h"

#ifdef H3
#include "h3.h"
#endif

void main()
{
}

(h1.h)

void f_h1()
{
}

(h2.h)

#define H3

(h3.h)

void f_h3()
{
}

Then I run pcpp a.c > pp.a.c, the result is:

#line 1 "h1.h"
void f_h1()
{
}
#line 1 "h3.h"
void f_h3()
{
}
#line 8 "a.c"
void main()
{
}

We can see, the macro H3 defined in h2.h is effective. But there's no trace of h2.h being processed in the final ouput pp.a.c file.

I compared it to the result of gcc, I run gccc -E a.c > gcc.pp.a.c, the result is:

# 1 "a.c"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "a.c"
# 1 "h1.h" 1
void f_h1()
{
}
# 2 "a.c" 2
# 1 "h2.h" 1 <================= HERE, the processing of h2.h is shown.
# 3 "a.c" 2


# 1 "h3.h" 1
void f_h3()
{
}
# 6 "a.c" 2


void main()
{
}

So I think maybe it is nice for pcpp to be more explicit to list the h2.h in the final output.

[ned14]

I've had a few people complain about this, even though this behaviour is perfectly standards conforming. I'll look into it.