There are much tools available that scans source code statically to find access errors and other problems. Have you looked at Lint?

Note that the generic C pointer is almost impossible to combine with range checking since it's intentionally allowed to support a lot of nice tricks. The next thing is that C can produce code quality quite close to assembler just because it maps so closely to real hardware. Having every pointer not only have an address, but also a step size and a min and max value, would help a lot. But the size of the pointer suddenly became several times larger. And it now requires a lot of registers, or memroy space, to transfer a pointer as a parameter or in a return. And all increments, decrements, general arithmetic, indirection etc must perform checks against these limits, making the code much larger. How fun would it be to test a 64kB program if you need a 128kB processor to be able to run the augmented binary?

Pascal is way easier to perform runtime checks on, since the amount of operations allowed on a pointer is way less.

The flexibility and efficiency is the strong side of C. But it's also the weak side. So if you add your runtime checking, you will have lost much of your flexibility and/or efficiency in which case C woldn't really have any strong points anymore. If the goal is Pascal with C syntax then it's better to just ignore the syntax issue and use Pascal from the start. Or move all the way to Ada. With ironclad descriptive declarations that doesn't allow dangerous constructs, you don't hardly need any runtime testing.