On 13 Nov 2017, at 23:41, Ben Coman <btc@openInWorld.com> wrote:

I have a C definition...

  unsigned long FPDF_GetLastError();

whose return values are...

  #define FPDF_ERR_SUCCESS 0    // No error.

  #define FPDF_ERR_UNKNOWN 1    // Unknown error.

  #define FPDF_ERR_FILE 2       // File not found or could not be opened.

  #define FPDF_ERR_FORMAT 3     // File not in PDF format or corrupted.

  #define FPDF_ERR_PASSWORD 4   // Password required or incorrect   password.

  #define FPDF_ERR_SECURITY 5   // Unsupported security scheme.

  #define FPDF_ERR_PAGE 6       // Page not found or content error.

I was thinking of turning those #define's into an FFIExternalEnumeration,

but I was wondering if I'll hit some undefined behaviour with the underlying representation being a "long" rather than an "int" ? 

I do see here that C enumerations can be a range of types including "long" 

* https://stackoverflow.com/questions/7093360/c-sharp-enum-of-long-values
but I'm not sure how it works in the Pharo context to know what the size underlying representation.

cheers -ben