Compiler allows out-of-bounds indexing, Stan programs seg-faulting

[mitzimorris]

Stan programs are segfaulting if user gets the indexing wrong.
Here's an example:

data {
  int<lower=0> N;               // number of items
  int<lower=0> M;               // number of predictors
  int<lower=0,upper=1> y[N];           // outcomes
  row_vector[M] x[N];      // predictors
}
transformed data {
  print(x[200,200]);
}

Given input where N=128 and M=2, print statement segfaults. The generated code should be checking bounds sized N,M before allowing access.

2 recent reports coming from CmdStanPy users confused by return code -11 -
https://discourse.mc-stan.org/t/cmdstanpy-error-code-11/21051/3
stan-dev/docs#228 (comment)

[bbbales2]

I think this is the same bug as #776.

[mitzimorris]

agreed, same bug as #776