Implicit declaration of function in C

Question

Is there any version of C, or any compiler that does not allow implicit declaration of functions?

For example. Using mingw compiler, if I use the printf function within my program without including stdio.h, it compiles my program, displaying a warning "incompatible implicit declaration of built-in function 'printf'".

i would like to know if there is some version of C, or some compiler, which does not compile my program in these situations.

Best regards.

Why not look at the various options available to the various compilers? Most allow you to make the warnings as errors — Ed Heal
– Ed Heal, Commented Apr 18, 2016 at 17:10
The 1999 standard did away with implicit int, so compiling with -std=c99 -Werror should catch any implicit declarations. — John Bode
– John Bode, Commented Apr 18, 2016 at 17:36
This is interesting. However, I am still interested in the original question. Is there any compiler that, in its standard operation, does not compile a program with implicit declaration? — Zaratruta
– Zaratruta, Commented Apr 18, 2016 at 17:37
The compiler has already issued a diagnostic for you. Ignoring this diagnostic means the program will have undefined behavior. Warnings should be treated as errors unless you never plan to change compilers or upgrade your compiler. — jxh
– jxh, Commented Apr 18, 2016 at 18:12

jdarthenay · Accepted Answer · 2016-04-18 17:13:21Z

1

When compiling use -Werror option and all warnings will be considered errors.

answered Apr 18, 2016 at 17:13

jdarthenay

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abhiarora · Accepted Answer · 2016-04-18 19:09:04Z

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You can use -Werror compiler option while compiling your code. It will consider all warning as error. I like to compile my source code using these option.

gcc -Wall -Werror -Wshadow -Wextra SOURCE.c -Wfloat-equal

answered Apr 18, 2016 at 19:09

abhiarora

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