What is the modulus of the libc pRNG LCG?

I'm a bit confused at the moment about the linear congruential generator used in the rand() function in stdlib to generate random numbers. The table on https://en.wikipedia.org/wiki/Linear_congruential_generator lists the modulus used by GCC and for ANSI C as 2^31. However, according to https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf p347, for ANSI C 2^32 is implicitly used. Does rand() in stdlib also use 2^32?

I've implemented and tested the ANSI C implementation, which works fine.