sample-hello

Sample "hello"

This is a primary and very simple example. Just compiles hello.c and generate a binary file hello.

This document gives you an overall guide:

• To compile a source file with ESSTRA Core applied to build a binary file with metadata embedded,
• To update license information in the metadata with an SPDX tag-value file generated with FOSSology,

and finally,

• To confirm that the license information is surely applied to the metadata in the binary file.

Notice

Each source file in this directory has an SPDX-License-Identifier: with some license ID, however, it's just for feasibility of this guide.

Though this directory contains a Makefile, we will explain what to do one by one precisely without using the Makefile.

Preparation

Before you begin this guide, install ESSTRA Core and ESSTRA Utility on your system by following How to Build and Install.

Build with ESSTRA Core

The file hello.c is a very simple C source file:

#include <stdio.h>

int main(void)
{
    printf("Hello, world!\n");
    return 0;
}

To compile hello.c with ESSTRA Core applied and generate a binary file named hello, type:

$ gcc -fplugin=/usr/local/share/esstra/esstracore.so hello.c -o hello

on the command line. If no errors, the file hello is generated.

Executing hello just displays a string Hello, world! on the standard output:

$ ./hello
Hello, world!

Note that compilation with ESSTRA Core applied does not affect the behavior of the resulting binary file at all.

Check What's Embedded

To display metadata embedded in the binary file hello, type:

$ esstar.py show hello

You can see a list of directories and files as well as SHA-1 hashes in YAML format. These files are all involved in the compilation of the file hello:

#
# BinaryFileName: output_example/hello
# BinaryPath: /home/snagao/esstra/samples/sample-hello/output_example/hello
#
---
SourceFiles:
  /home/snagao/esstra/samples/sample-hello:
  - File: hello.c
    SHA1: 62592ce351eab2dfb75deb8c01101e07d6fe3c67
  /usr/include:
  - File: features-time64.h
    SHA1: 57c3c8093c3af70e5851f6d498600e2f6e24fdeb
  - File: features.h
    SHA1: d8725bb98129d6d70ddcbf010021c2841db783f7
  - File: stdc-predef.h
    SHA1: 2fef05d80514ca0be77efec90bda051cf87d771f
  - File: stdio.h
    SHA1: c7181b48c4194cd122024971527aab4056baf600
  /usr/include/x86_64-linux-gnu/bits:
  - File: typesizes.h
    SHA1: ee94b5a60d007c23bdda9e5c46c8ba40f4eb402c
  - File: wordsize.h
    SHA1: 281ddd3c93f1e8653e809a45b606574c9b691092
  /usr/include/x86_64-linux-gnu/bits/types:
  - File: FILE.h
    SHA1: 497924e329d53517631713ae52acb73e870d7d65
  - File: __FILE.h
    SHA1: 274242343e85d1c06e7f5ccc5abf15e120f6e957
  - File: __fpos64_t.h
    SHA1: ac38e294b004f6e2bf18f1c55e03dc80f48d6830
  - File: __fpos_t.h
    SHA1: 760ef77769ac1921f4b1f908cbf06863e2506775
  - File: __mbstate_t.h
    SHA1: e3a4f2ee55e635520db0b4610d2b361e9ce41de7
  - File: struct_FILE.h
    SHA1: 1dbf8bac589cb09e09aa4c1d36913e549a57bcf0
  /usr/include/x86_64-linux-gnu/gnu:
  - File: stubs-64.h
    SHA1: f7603fa3908b56e9d1b33c91590db3252e13a799
  - File: stubs.h
    SHA1: be168037b7503a82b1cf694cdbac8c063bb6e476
  /usr/include/x86_64-linux-gnu/sys:
  - File: cdefs.h
    SHA1: a419a6372029d89ba38ada0811d34f51df8d09b7
  /usr/lib/gcc/x86_64-linux-gnu/11/include:
  - File: stdarg.h
    SHA1: fa23f49da8a0a5068b781dff7182f1a1c363dc30
  - File: stddef.h
    SHA1: 0de70008ffa3f198baf55c7b3f3d03b4ca11c21f

Generate SPDX File with FOSSology

One of the features of ESSTRA is to attach license information to metadata by the ESTTRA Utility's command update as mentioned here.

Prebuilt Files

For reference, a prebuilt binary file hello is placed in the sub directory output_example, which was built on our development environment mentioned in the README.md file in the top directory.