make the result of the cimag macro a non-lvalue

this change is not necessary but helps diagnose invalid code. based on
patch by Jens Gustedt.

diff --git a/include/complex.h b/include/complex.h
index 23bab7d5593042e3c878707ad22dc86cdb843a1d..bdddf87bbd312e1a901a7c529c4fa42ccbd02e1a 100644 (file)
--- a/include/complex.h
+++ b/include/complex.h
@@ -103,7 +103,7 @@ long double creall(long double complex);
 
 #ifndef __cplusplus
 #define __CIMAG(x, t) \
-       ((union { _Complex t __z; t __xy[2]; }){(_Complex t)(x)}.__xy[1])
+       (+(union { _Complex t __z; t __xy[2]; }){(_Complex t)(x)}.__xy[1])
 
 #define creal(x) ((double)(x))
 #define crealf(x) ((float)(x))