[Bug preprocessor/112978] New: Five minute long error message when OpenMP pragma is erroneously placed in macro

[Bug preprocessor/112978] New: Five minute long error message when OpenMP pragma is erroneously placed in macro

[raymondkenchang at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112978

            Bug ID: 112978
           Summary: Five minute long error message when OpenMP pragma is
                    erroneously placed in macro
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: preprocessor
          Assignee: unassigned at gcc dot gnu.org
          Reporter: raymondkenchang at gmail dot com
  Target Milestone: ---

When an OpenMP pragma is placed in a macro definition incorrectly, the error
message is extremly long. It took 5 minutes on my machine to output. 

```

```

```
./compilers/gcc_install/bin/gcc -c -fopenmp hello.c  23.68s user 8.56s system
10% cpu 5:06.35 total
```

Test case:
```
#define LIM1(x) x##0, x##1, x##2, x##3, x##4, x##5, x##6, x##7, x##8, x##9,
#define LIM2(x) LIM1(x##0) LIM1(x##1) LIM1(x##2) LIM1(x##3) LIM1(x##4) \
                LIM1(x##5) LIM1(x##6) LIM1(x##7) LIM1(x##8) LIM1(x##9)
#define LIM3(x) LIM2(x##0) LIM2(x##1) LIM2(x##2) LIM2(x##3) LIM2(x##4) \
                LIM2(x##5) LIM2(x##6) LIM2(x##7) LIM2(x##8) LIM2(x##9)
#define LIM4(x) LIM3(x##0) LIM3(x##1) LIM3(x##2) LIM3(x##3) LIM3(x##4) \
                LIM3(x##5) LIM3(x##6) LIM3(x##7) LIM3(x##8) LIM3(x##9)
#define LIM5(x) LIM4(x##0) LIM4(x##1) LIM4(x##2) LIM4(x##3) LIM4(x##4) \
                LIM4(x##5) LIM4(x##6) LIM4(x##7) LIM4(x##8) LIM4(x##9)
#define LIM6(x) LIM5(x##0) LIM5(x##1) LIM5(x##2) LIM5(x##3) LIM5(x##4) \
#pragma omp barrier
                LIM5(x##5) LIM5(x##6) LIM5(x##7) LIM5(x##8) LIM5(x##9)
#define LIM7(x) LIM6(x##0) LIM6(x##1) LIM6(x##2) LIM6(x##3) LIM6(x##4) \
                LIM6(x##5) LIM6(x##6) LIM6(x##7) LIM6(x##8) LIM6(x##9)

enum q21_enum
{
  LIM5 (e)
};
```

[Bug preprocessor/112978] Five minute long error message when OpenMP pragma is erroneously placed in macro

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112978

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |compile-time-hog

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I doubt this is fixable really because the number of expansions is huge.

[Bug preprocessor/112978] Five minute long error message when OpenMP pragma is erroneously placed in macro

[raymondkenchang at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112978

--- Comment #2 from Raymond Chang <raymondkenchang at gmail dot com> ---
(In reply to Andrew Pinski from comment #1)
> I doubt this is fixable really because the number of expansions is huge.

Thanks, I think this is a pretty uncommon situtation anyways. I figured I'd
report it anyways though.

[Bug preprocessor/112978] Five minute long error message when OpenMP pragma is erroneously placed in macro

[xry111 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112978

Xi Ruoyao <xry111 at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
                 CC|                            |xry111 at gcc dot gnu.org
         Resolution|---                         |WONTFIX

--- Comment #3 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
There is nothing we can do here.

Note that GCC security policy is clear that if you need to compile some random
code completely not trust-able, use a sandbox.

And for "excessive amount of diagnostics" you may use -fmax-errors= as a
workaround.