Ramon Diaz-Uriarte wrote on 03/05/2008 04:25 AM: > Dear All, > > In a package, I want to use some C code where I am using a structure > (as the basic element of a linked list) with flexible array members. > Basically, this is a structure where the last component is an > incomplete array type (e.g., Harbison & Steel, "C, a reference > manual, 5th ed.", p. 159) such as: > > struct Sequence { > struct Sequence *next; > int len; > unsigned int state_count[]; > }; > > > To create one such sequence, I allocate storage (following Harbison > and Steel) in a C program as follows: > > struct Sequence *A; > int n = 4; > A = malloc( sizeof(struct Sequence) + n * sizeof(unsigned int)); > > > If I understand correctly, however, it would be better to use R_alloc > instead of malloc (memory automagically freed on exit and error; > error-checking). But I do not know how to make the call to R_alloc > here, since R_alloc allocates n units of size bytes each. > > > I've tried, without success, the following two: > > int to_add_for_R_alloc = > (int) ceil((float) sizeof(struct sequence) / sizeof(unsigned int)); > > A = (struct sequence *) R_alloc(to_add_for_R_alloc + n, > sizeof(unsigned int)); > > or even a brute force attempt as: > > A = (struct sequence *) R_alloc( 100, sizeof(struct sequence)); > > > but both result in segmentation faults. > > > Should I just keep using malloc (and free at end)?
Hi Ramon, You should be able to use R_alloc without seg faults, so there's something wrong with your code somewhere. R_alloc multiplies its arguments together to come up with the total number of bytes to allocate then it allocates a raw vector and returns the data portion. So you can just treat R_alloc similarly to malloc by calling R_alloc(1,sizeof(struct Sequence) + n * sizeof(unsigned int)). Best, Jeff -- http://biostat.mc.vanderbilt.edu/JeffreyHorner ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.