First C compiler ported to GCC

Post by pjmlp » Wed, Apr 07, 2021, 12:28 PM UTC

st_goliath wrote: post #60

pjmlp wrote: post #57

Earlier quoted context omitted.

https://www.bell-labs.com/usr/dmr/www/chist.html > To encourage people to pay more attention to the official language rules, to detect legal but suspicious constructions, and to help find interface mismatches undetectable with simple mechanisms for separate compilation, Steve Johnson adapted his pcc compiler to produce lint [Johnson 79b], which scanned a set of files and remarked on dubious constructions.

Yes, I'm not arguing against such warnings in general. I'm arguing against pure coding style type warnings. Here's an example: If you do an '==' comparison inside an if, you might accidentally type '=' instead, making it a perfectly valid assignment. The gcc developers eventually decided to issue a warning if you do an assignment inside an 'if' conditional, but give you the option to put another set of parantheses ar…

Post by Koshkin » Wed, Apr 07, 2021, 12:33 PM UTC

mschuster91 wrote: post #58

charcircuit wrote: post #54

Earlier quoted context omitted.

Not everything needs a valid use case. It can exist just for fun.

The thing is, the more complex a spec is (or rather, how much stuff it allows that will never be used), the bigger the danger is that somewhen down the line, this will introduce a security or other issue.

Post by quotemstr » Wed, Apr 07, 2021, 1:17 PM UTC

st_goliath wrote: post #35

raverbashing wrote: post #33

Earlier quoted context omitted.

Hence why it "can be written" as b[a] as well Edit: it doesn't blow up, not even with -Wall and -std=c99

> (yes it will probably blow up in modern compilers, or at least give you a warning) Nope. For the code snippet I posted an hour ago, even with -pedantic -Wall -Wextra gcc won't issue any warnings. And why should it? It's perfectly standards conformant, because the standard actually defines the [] operator through the equivalent addition expression.

Post by chrisseaton » Wed, Apr 07, 2021, 2:05 PM UTC

mschuster91 wrote: post #64

Koshkin wrote: post #63

Earlier quoted context omitted.

I think the assumption that addition is commutative in any context simplifies the spec rather than makes it more complex.

It however is not "natural" for someone who doesn't know the obscure bits of history in a standard written many decades ago. Someone writing, say, a static code analysis tool or an IDE may not assume that it is possible that in the expression `a[b]` a may be something else than a pointer / array.

Post by IncRnd » Wed, Apr 07, 2021, 2:16 PM UTC

29athrowaway wrote: post #10

If the first C compiler was written in C... how could it be first C compiler? How could you compile the first C compiler?