To #include a C library into an Arduino program

Hi, I am trying to #include a C library into an Arduino program. The code works well in standard C/C++ environment, but when the code is transplanted into Arduino, the IDE can never recognize any variables or functions declared in the library's head file.
I am wondering whether standard C/C++ library may be directly used by Arduino or it is necessary to make any syntactic change? Anyone may help? Thanks in advance.

Did u use int? Ardunio often messes up

Might depend on the library. Remind us which library this is again?

Syntax is the same. Post more detailed info.

Let me know which library your using,.

Thanks, the library I am trying to #include is Libcurl (http://curl.haxx. se/), #include <curl/curl.h> is declared in the Arduino program, as I did in the C, but nothing from the library is recognized by Arduino IDE, reported errors are like – “error: ‘CURL’ was not declared in this scope” or “error: ‘curl_easy_setopt’ was not declared in this scope”, although those items are well declared in the head file. Do you have any idea? Thanks.

Custom libraries you have to place into folder ..libraries*name_of_library* otherwise it couldn't find it.

Budvar10:
Custom libraries you have to place into folder ..libraries*name_of_library* otherwise it couldn't find it.

Thanks, I have noticed the necessity and followed the suit. The IDE does not say the head file is not found, but just list all items declared in the head file as "not declared". It is really puzzling.

COLDMOUNT:

Budvar10:
Custom libraries you have to place into folder ..libraries*name_of_library* otherwise it couldn't find it.

Thanks, I have noticed the necessity and followed the suit. The IDE does not say the head file is not found, but just list all items declared in the head file as "not declared". It is really puzzling.

Moreover, a C/C++ library is usually not clearly formed as that of Arduino. Each arduino library usually only include two files, like Servo.h & Servo.cpp, but C/C++ libraries are more chaotic. Does that make the problem?

COLDMOUNT:
Thanks, I have noticed the necessity and followed the suit.

Please give more details of the actual file name(s) and location(s). Note that due to the peculiar method the Arduino IDE uses to build your sketch, the library must contain a header file which matches the name of the directory the library implementation is stored in, plus a .h suffix, and this header must be included in your sketch.

libcurl is ~300KB in size. How do you expect to fit that into an Arduino?