Including one C source file in another

Question

Is it OK  or even recommended good practice  to  include a  c file in another  c file

User · Answer

The extension of the file does not matter to most C compilers, so it will work.

However, depending on your makefile or project settings the included c file might generate a separate object file. When linking that might lead to double defined symbols.

User · Answer

The extension of the file does not matter to most C compilers, so it will work.

However, depending on your makefile or project settings the included c file might generate a separate object file. When linking that might lead to double defined symbols.

User · Answer

Used properly  this can be a useful technique   Say you have a complex  performance critical subsystem with a fairly small public interface and a lot of non-reusable implementation code  The code runs to several thousand lines  a hundred or so private functions and quite a bit of private data  If you work with non-trivial embedded systems  you probably deal with this situation frequently enough   Your solution will probably be layered  modular and decoupled and these aspects can be usefully represented and reinforced by coding different parts of the subsystem in different files    With C  you can lose a lot by doing this  Almost all toolchains provide decent optimisation for a single compilation unit  but are very pessimistic about anything declared extern   If you put everything into one C source module  you get -   Performance  amp  code size improvements - function calls will be inlined in many cases  Even without inlining  the compiler has opportunities to produce more efficient code  Link level data  amp  function hiding  Avoidance of namespace pollution and its corollary - you can use less unwieldy names  Faster compilation  amp  linkage    But you also get an unholy mess when it comes to editing this file and you lose the implied modularity  This can be overcome by splitting the source into several files and including these to produce a single compilation unit   You need to impose some conventions to manage this properly though  These will depend on your toolchain to some extent  but some general pointers are -   Put the public interface in a separate header file - you should be doing this anyway  Have one main  c file that includes all the subsidiary  c files  This could also include the code for the public interface  Use compiler guards to ensure that private headers and source modules are not included by external compilation units  All private data  amp  functions should be declared static  Maintain the conceptual distinction between  c and  h files  This leverages existing conventions  The difference is that you will have a lot of static declarations in your headers  If your toolchain doesn t impose any reason not to  name the private implementation files as  c and  h  If you use include guards  these will produce no code and introduce no new names  you may end up with some empty segments during linkage   The huge advantage is that other tools  e g  IDEs  will treat these files appropriately

User · Answer

Including C file into another file is legal  but not advisable thing to do  unless you know exactly why are you doing this and what are you trying to achieve  I m almost sure that if you will post here the reason that behind your question the community will find you another more appropriate way to achieve you goal  please note the  almost   since it is possible that this is the solution given the context       By the way i missed the second part of the question  If C file is included to another file and in the same time included to the project you probably will end up with duplicate symbol problem why linking the objects  i e same function will be defined twice  unless they all static

User · Answer

you should add header like this   include  lt another c gt    note   both file should placed in same place  i use this in codevison AVR for ATMEGA micro controllers and work truly but its not work in normal C language file

User · Answer

Used properly  this can be a useful technique   Say you have a complex  performance critical subsystem with a fairly small public interface and a lot of non-reusable implementation code  The code runs to several thousand lines  a hundred or so private functions and quite a bit of private data  If you work with non-trivial embedded systems  you probably deal with this situation frequently enough   Your solution will probably be layered  modular and decoupled and these aspects can be usefully represented and reinforced by coding different parts of the subsystem in different files    With C  you can lose a lot by doing this  Almost all toolchains provide decent optimisation for a single compilation unit  but are very pessimistic about anything declared extern   If you put everything into one C source module  you get -   Performance  amp  code size improvements - function calls will be inlined in many cases  Even without inlining  the compiler has opportunities to produce more efficient code  Link level data  amp  function hiding  Avoidance of namespace pollution and its corollary - you can use less unwieldy names  Faster compilation  amp  linkage    But you also get an unholy mess when it comes to editing this file and you lose the implied modularity  This can be overcome by splitting the source into several files and including these to produce a single compilation unit   You need to impose some conventions to manage this properly though  These will depend on your toolchain to some extent  but some general pointers are -   Put the public interface in a separate header file - you should be doing this anyway  Have one main  c file that includes all the subsidiary  c files  This could also include the code for the public interface  Use compiler guards to ensure that private headers and source modules are not included by external compilation units  All private data  amp  functions should be declared static  Maintain the conceptual distinction between  c and  h files  This leverages existing conventions  The difference is that you will have a lot of static declarations in your headers  If your toolchain doesn t impose any reason not to  name the private implementation files as  c and  h  If you use include guards  these will produce no code and introduce no new names  you may end up with some empty segments during linkage   The huge advantage is that other tools  e g  IDEs  will treat these files appropriately

User · Answer

is it ok  yes  it will compile  is it recommended  no -  c files compile to  obj files  which are linked together after compilation  by the linker  into the executable  or library   so there is no need to include one  c file in another  What you probably want to do instead is to make a  h file that lists the functions variables available in the other  c file  and include the  h file

User · Answer

No   Depending on your build environment  you don t specify   you may find that it works in exactly the way that you want   However  there are many environments  both IDEs and a lot of hand crafted Makefiles  that expect to compile   c - if that happens you will probably end up with linker errors due to duplicate symbols   As a rule this practice should be avoided   If you absolutely must  include source  and generally it should be avoided   use a different file suffix for the file

User · Answer

You can use the gcc compiler in linux to link two c file in one output  Suppose you have two c files one is  main c  and another is  support c   So the command to link these two is  gcc main c support c -o main out   By this two files will be linked to a single output main out To run the output the command will be    main out   If you are using function in main c which is declared in support c file then you should declare it in main also using extern storage class

User · Answer

The extension of the file does not matter to most C compilers, so it will work.

However, depending on your makefile or project settings the included c file might generate a separate object file. When linking that might lead to double defined symbols.

User · Answer

Numerous other answers have more than covered how you can do this but why you probably should not in normal circumstances  That said  I will add why I ve done it in the past  In embedded development  it s common to have silicon vendor source code as part of your compiled files  The problem is those vendors likely don t have the same style guides or standard warning error flag settings as your organization  So  you can create a local source file that includes the vendor source code and then compile this wrapper C file instead to suppress any issues in the included source as well as any headers included by that source  As an example          file   vendor wrap c     brief  vendor source code wrapper to prevent warnings      pragma GCC diagnostic push  pragma GCC diagnostic ignored  quot -Wnested-externs quot   include  quot vendor source code c quot   pragma GCC diagnostic pop  This allows you to use less complicated Make scripting with a standard set of compiler flags and settings with specific exceptions in the code rather than have custom flags for some files in the scripting  gcc main c vendor wrap c -o   CFLAGS  main out

User · Answer

The C language doesn t prohibit that kind of  include  but the resulting translation unit still has to be valid C   I don t know what program you re using with a  prj file   If you re using something like  make  or Visual Studio or whatever  just make sure that you set its list of files to be compiled without the one that can t compile independently

User · Answer

Including C file into another file is legal  but not advisable thing to do  unless you know exactly why are you doing this and what are you trying to achieve  I m almost sure that if you will post here the reason that behind your question the community will find you another more appropriate way to achieve you goal  please note the  almost   since it is possible that this is the solution given the context       By the way i missed the second part of the question  If C file is included to another file and in the same time included to the project you probably will end up with duplicate symbol problem why linking the objects  i e same function will be defined twice  unless they all static

User · Answer

I thought I d share a situation where my team decided to include  c files   Our archicture largely consists of modules that are decoupled through a message system   These message handlers are public  and call many local static worker functions to do their work   The problem came about when trying to get coverage for our unit test cases  as the only way to exercise this private implementation code was indirectly through the public message interface   With some worker functions knee-deep in the stack  this turned out to be a nightmare to achieve proper coverage   Including the  c files gave us a way to reach the cog in the machine we were interesting in testing

User · Answer

The C language doesn t prohibit that kind of  include  but the resulting translation unit still has to be valid C   I don t know what program you re using with a  prj file   If you re using something like  make  or Visual Studio or whatever  just make sure that you set its list of files to be compiled without the one that can t compile independently

User · Answer

Including C file into another file is legal  but not advisable thing to do  unless you know exactly why are you doing this and what are you trying to achieve  I m almost sure that if you will post here the reason that behind your question the community will find you another more appropriate way to achieve you goal  please note the  almost   since it is possible that this is the solution given the context       By the way i missed the second part of the question  If C file is included to another file and in the same time included to the project you probably will end up with duplicate symbol problem why linking the objects  i e same function will be defined twice  unless they all static

User · Answer

The extension of the file does not matter to most C compilers, so it will work.

However, depending on your makefile or project settings the included c file might generate a separate object file. When linking that might lead to double defined symbols.

User · Answer

you should add header like this   include  lt another c gt    note   both file should placed in same place  i use this in codevison AVR for ATMEGA micro controllers and work truly but its not work in normal C language file

User · Answer

You can properly include  C or  CPP files into other source files  Depending on your IDE  you can usually prevent double-linkage by looking at the source files properties you want to be included  usually by right clicking on it and clicking properties  and uncheck check compile link exclude from build or whatever option it may be  Or you could not include the file in the project itself  thus the IDE wont even know it exists and wont try to compile it  And with makefiles you simply just wouldn t put the file in it for compiling and linking    EDIT  Sorry I made it an answer instead of a reply onto other answers

User · Answer

is it ok  yes  it will compile  is it recommended  no -  c files compile to  obj files  which are linked together after compilation  by the linker  into the executable  or library   so there is no need to include one  c file in another  What you probably want to do instead is to make a  h file that lists the functions variables available in the other  c file  and include the  h file

User · Answer

I thought I d share a situation where my team decided to include  c files   Our archicture largely consists of modules that are decoupled through a message system   These message handlers are public  and call many local static worker functions to do their work   The problem came about when trying to get coverage for our unit test cases  as the only way to exercise this private implementation code was indirectly through the public message interface   With some worker functions knee-deep in the stack  this turned out to be a nightmare to achieve proper coverage   Including the  c files gave us a way to reach the cog in the machine we were interesting in testing

User · Answer

No   Depending on your build environment  you don t specify   you may find that it works in exactly the way that you want   However  there are many environments  both IDEs and a lot of hand crafted Makefiles  that expect to compile   c - if that happens you will probably end up with linker errors due to duplicate symbols   As a rule this practice should be avoided   If you absolutely must  include source  and generally it should be avoided   use a different file suffix for the file

User · Answer

is it ok  yes  it will compile  is it recommended  no -  c files compile to  obj files  which are linked together after compilation  by the linker  into the executable  or library   so there is no need to include one  c file in another  What you probably want to do instead is to make a  h file that lists the functions variables available in the other  c file  and include the  h file

User · Answer

The C language doesn t prohibit that kind of  include  but the resulting translation unit still has to be valid C   I don t know what program you re using with a  prj file   If you re using something like  make  or Visual Studio or whatever  just make sure that you set its list of files to be compiled without the one that can t compile independently

User · Answer

is it ok  yes  it will compile  is it recommended  no -  c files compile to  obj files  which are linked together after compilation  by the linker  into the executable  or library   so there is no need to include one  c file in another  What you probably want to do instead is to make a  h file that lists the functions variables available in the other  c file  and include the  h file

User · Answer

The C language doesn t prohibit that kind of  include  but the resulting translation unit still has to be valid C   I don t know what program you re using with a  prj file   If you re using something like  make  or Visual Studio or whatever  just make sure that you set its list of files to be compiled without the one that can t compile independently

User · Answer

You can use the gcc compiler in linux to link two c file in one output  Suppose you have two c files one is  main c  and another is  support c   So the command to link these two is  gcc main c support c -o main out   By this two files will be linked to a single output main out To run the output the command will be    main out   If you are using function in main c which is declared in support c file then you should declare it in main also using extern storage class

User · Answer

Numerous other answers have more than covered how you can do this but why you probably should not in normal circumstances  That said  I will add why I ve done it in the past  In embedded development  it s common to have silicon vendor source code as part of your compiled files  The problem is those vendors likely don t have the same style guides or standard warning error flag settings as your organization  So  you can create a local source file that includes the vendor source code and then compile this wrapper C file instead to suppress any issues in the included source as well as any headers included by that source  As an example          file   vendor wrap c     brief  vendor source code wrapper to prevent warnings      pragma GCC diagnostic push  pragma GCC diagnostic ignored  quot -Wnested-externs quot   include  quot vendor source code c quot   pragma GCC diagnostic pop  This allows you to use less complicated Make scripting with a standard set of compiler flags and settings with specific exceptions in the code rather than have custom flags for some files in the scripting  gcc main c vendor wrap c -o   CFLAGS  main out

User · Answer

No   Depending on your build environment  you don t specify   you may find that it works in exactly the way that you want   However  there are many environments  both IDEs and a lot of hand crafted Makefiles  that expect to compile   c - if that happens you will probably end up with linker errors due to duplicate symbols   As a rule this practice should be avoided   If you absolutely must  include source  and generally it should be avoided   use a different file suffix for the file

User · Answer

You can properly include  C or  CPP files into other source files  Depending on your IDE  you can usually prevent double-linkage by looking at the source files properties you want to be included  usually by right clicking on it and clicking properties  and uncheck check compile link exclude from build or whatever option it may be  Or you could not include the file in the project itself  thus the IDE wont even know it exists and wont try to compile it  And with makefiles you simply just wouldn t put the file in it for compiling and linking    EDIT  Sorry I made it an answer instead of a reply onto other answers

User · Answer

No   Depending on your build environment  you don t specify   you may find that it works in exactly the way that you want   However  there are many environments  both IDEs and a lot of hand crafted Makefiles  that expect to compile   c - if that happens you will probably end up with linker errors due to duplicate symbols   As a rule this practice should be avoided   If you absolutely must  include source  and generally it should be avoided   use a different file suffix for the file

User · Answer

Including C file into another file is legal  but not advisable thing to do  unless you know exactly why are you doing this and what are you trying to achieve  I m almost sure that if you will post here the reason that behind your question the community will find you another more appropriate way to achieve you goal  please note the  almost   since it is possible that this is the solution given the context       By the way i missed the second part of the question  If C file is included to another file and in the same time included to the project you probably will end up with duplicate symbol problem why linking the objects  i e same function will be defined twice  unless they all static

[c] Including one C source file in another?

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