GCC #pragma to stop compilation

Question

Is there a GCC pragma directive that will stop, halt, or abort the compilation process?

I am using GCC 4.1, but I would want the pragma to be available in GCC 3.x versions also.

We might be able to provide a better answer if you tell us why you want compilation to stop. — Michael, Jan 23 '10 at 22:22

Dirk Eddelbuettel · Accepted Answer · 2021-11-14T23:50:51.620

61

You probably want #error:

$ cd /tmp
$ g++ -Wall -DGoOn -o stopthis stopthis.cpp
$ ./stopthis

Hello, world

$ g++ -Wall -o stopthis stopthis.cpp

stopthis.cpp:7:6: error: #error I had enough

File stopthis.cpp

#include <iostream>

int main(void) {
  std::cout << "Hello, world\n";
  #ifndef GoOn
    #error I had enough
  #endif
  return 0;
}

edited Nov 14 '21 at 23:50

answered Jan 23 '10 at 22:23

Dirk Eddelbuettel

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A limitation here is `#error` can't be used inside a macro, though the question is vague as to the purpose. – ideasman42 Aug 01 '14 at 10:03
6

I thought this too, however my GCC (4.9) isn't stopping with an error, it carries on, obviously it doesn't compile but it doesn't halt, is this a bug or can you confirm? – Alec Teal Jan 15 '16 at 23:53

score 21 · Answer 2 · edited Nov 14 '21 at 22:40

21

I do not know about a #pragma, but #error should do what you want:

#error Failing compilation

It will terminate compilation with the error message "Failing compilation".

edited Nov 14 '21 at 22:40

Peter Mortensen

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answered Jan 23 '10 at 22:21

Michael

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score 13 · Answer 3 · edited Nov 14 '21 at 22:52

13

This works:

 #include <stophere>

GCC stops when it can't find the include file. I wanted GCC to stop if C++14 was not supported.

 #if __cplusplus<201300L
   #error need g++14
   #include <stophere>
#endif

edited Nov 14 '21 at 22:52

Peter Mortensen

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answered Aug 13 '17 at 13:58

mosh

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This is the best answer. It prevents the compiler from continuing and potentially spamming lots of unhelpful errors that occur after the #error. Those later errors may be misleading to some since they are likely just side effects of the first error. – phatpaul Feb 24 '23 at 14:42

score 6 · Answer 4 · edited Nov 14 '21 at 22:45

While typically #error is sufficient (and portable), there are times when you want to use a pragma, namely, when you want to optionally cause an error within a macro.

Here is an example use which depends on C11's _Generic and _Pragma.

This example ensures var isn't an int * or a short *, but not a const int * at compile time.

Example:

#define MACRO(var)  do {  \
    (void)_Generic(var,   \
          int       *: 0, \
          short     *: 0, \
          const int *: 0 _Pragma("GCC error \"const not allowed\""));  \
    \
    MACRO_BODY(var); \
} while (0)

score 3 · Answer 5 · edited Nov 14 '21 at 22:47

3

#pragma GCC error "error message"

Ref: 7 Pragmas

edited Nov 14 '21 at 22:47

Peter Mortensen

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answered Jan 10 '15 at 22:35

Leo

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score 0 · Answer 6 · edited Nov 14 '21 at 22:54

0

You can use:

#pragma GCC error "my message"

But it is not standard.

edited Nov 14 '21 at 22:54

Peter Mortensen

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answered Sep 10 '17 at 10:08

Klevh

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score 0 · Answer 7 · answered Jan 02 '23 at 08:02

0

An alternative is to use static_assert:

#if defined(_MSC_VER) && _MSC_VER < 1916
    static_assert(false, "MSVC supported versions are 1916 and later");
#endif

answered Jan 02 '23 at 08:02

Aykhan Hagverdili

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GCC #pragma to stop compilation

7 Answers7

File stopthis.cpp

Linked