Section 6.5.2.5 of the ISO/IEC 9899:1999 (C99) standard defines a compound literal (CL) as:

A postfix expression that consists of a parenthesized type name followed by a brace-enclosed list of initializers ... The value of a compound literal is that of an unnamed object initiated by the initializer list

The storage for this object is either static if the CL occurs compound literaloccurs at file scope or automatic if the CL compound literal occurs at block scope (6.5.2.5.6).

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It should be noted that only one object is created per CL compound literal -- even if the CL compound literal appears in a loop and has dynamic initializers (6.5.2.5.16). This can lead to incorrect use, as demonstrated below.

Noncompliant Code Example

In this thenoncompliant followingcode example, an array of pointers is filled with what appear to addresses of distinct {{INT_STRUCT}} objects, one for each integer in the range \[0,MAX_INTS-1\]:

#include <stdio.h>

typedef struct INT_STRUCT{
  int x;
} INT_STRUCT;

#define MAX_INTS 10
int main(int argc, char **argv){
  int i;
  INT_STRUCT *ints[MAX_INTS];
  for (i = 0;i<MAX i < MAX_INTS; i++)
    ints[i] = &(INT_STRUCT){i};
  for (i=0;i<MAX_INTS;i++)
    printf("%d\n",ints[i]->x);
}

However, only one INT_STRUCT object is actually created. At each iteration of the first loop, the "x" member of this object is set equal to the current value of the loop counter , "i". Therefore, after the first loop terminates, the value of the "x" member is MAX_INTS - 1.

During the print loop, this value is printed MAX_INTS times because every pointer in the "ints" array is set to point to the (single) INT_STRUCT object.

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