[Issue 24620] New: ImportC: can't compile cJSON

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24620

          Issue ID: 24620
           Summary: ImportC: can't compile cJSON
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: ryuukk.dev at gmail.com

clone: https://github.com/DaveGamble/cJSON

create: 'it.c' (otherwise it complains about `main.d(5): Error: import
`main.cJSON` is used as a type`)

```
#include "cJSON.c"
```

create: 'main.d'

```D
import it;

void main()
{
    cJSON* request = cJSON_Parse(null);
}
```

compile&run: 'dmd main.d it.c -of=bug && ./bug'
```
$ dmd main.d it.c -of=bug && ./bug
In file included from <command-line>:                                           
/usr/include/dlang/dmd/importc.h:101:8: warning: undefining "__has_feature"     
  101 | #undef __has_feature                                                    
      |        ^~~~~~~~~~~~~                                                    
/usr/include/dlang/dmd/importc.h:104:8: warning: undefining "__has_extension"   
  104 | #undef __has_extension                                                  
      |        ^~~~~~~~~~~~~~~                                                  
cJSON.c(569): Error: undefined identifier `__builtin_isinf_sign`
cJSON.c(1205): Error: `buffer` is not a member of `printbuffer[1]`
cJSON.c(1206): Error: `length` is not a member of `printbuffer[1]`
cJSON.c(1207): Error: `format` is not a member of `printbuffer[1]`
cJSON.c(1208): Error: `hooks` is not a member of `printbuffer[1]`
cJSON.c(1228): Error: `buffer` is not a member of `printbuffer[1]`
cJSON.c(1242): Error: `buffer` is not a member of `printbuffer[1]`
cJSON.c(1251): Error: `buffer` is not a member of `printbuffer[1]`
```

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