4 ms·

Your claim is actually false. C differentiates between a conforming program and a strictly conforming program. 5.1.2.3 binds to conforming programs which is per

by Kranar 4y ago

Your claim is actually false. C differentiates between a conforming program and a strictly conforming program. 5.1.2.3 binds to conforming programs which is permitted to produce output dependent on undefined behavior. Only strictly conforming programs may not produce output dependent on undefined behavior.

AlotOfReading 4y ago
No? Conformance allows unspecified and implementation defined. Strict conformance is the absence of that (i.e. same output in every conforming environment). Neither includes UB, as UB is "outside the standard" in some sense and doesn't have defined semantics.
- Kranar 4y ago
  It's a common misconception that a conforming program may not engender undefined behavior. In fact this very article touches on how realloc has introduced new (and backwards incompatible) undefined behavior precisely to accommodate the POSIX standard (so that POSIX compliant implementations of C can redefine the otherwise undefined behavior however they please).
  - AlotOfReading 4y ago
    Can you cite that? It runs against a plain reading of the standards (both C and C++) and would be insane for the standard to allow "correct" programs to include those with undefined behavior. There was even an unadopted proposal (n853 [1]) attempting to clarify this. While I was making sure I wasn't missing something obvious, I took a look through the rest of the WG14 proposals to see if I was somehow off in my understanding regarding translators being allowed to barf over UB anywhere in the program. There was a proposal clarifying the situation to the possible-execution understanding from upthread submitted by Victor Yodaiken (n2278 [2]), but unfortunately it was also never adopted. [1] https://www.open-std.org/jtc1/sc22/wg14/www/docs/n853.htm https://www.open-std.org/jtc1/sc22/wg14/www/docs/n853.htm [2] https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2278.pdf https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2278.pdf
    - Kranar 4y ago
      You are now mixing correct and conforming programs. Neither the C or C++ Standard mention anything involving correct programs. C uses the term conforming program and C++ uses the term well-formed program. In C a conforming program is any program that satisfies any single conforming implementation, even if said implementation includes extensions or non-portable constructs. A strictly conforming program is a program that satisfies every conforming implementation, which implies that said program does not produce an output that depends on undefined, unspecified, or implementation defined behavior. In C++ a well-formed program is any program that satisfies the syntax rules, diagnosable semantic rules and the one-definition rule.

by Kranar 4y ago

AlotOfReading 4y ago

No? Conformance allows unspecified and implementation defined. Strict conformance is the absence of that (i.e. same output in every conforming environment). Neither includes UB, as UB is "outside the standard" in some sense and doesn't have defined semantics.

Kranar 4y ago
It's a common misconception that a conforming program may not engender undefined behavior. In fact this very article touches on how realloc has introduced new (and backwards incompatible) undefined behavior precisely to accommodate the POSIX standard (so that POSIX compliant implementations of C can redefine the otherwise undefined behavior however they please).
- AlotOfReading 4y ago
  Can you cite that? It runs against a plain reading of the standards (both C and C++) and would be insane for the standard to allow "correct" programs to include those with undefined behavior. There was even an unadopted proposal (n853 [1]) attempting to clarify this. While I was making sure I wasn't missing something obvious, I took a look through the rest of the WG14 proposals to see if I was somehow off in my understanding regarding translators being allowed to barf over UB anywhere in the program. There was a proposal clarifying the situation to the possible-execution understanding from upthread submitted by Victor Yodaiken (n2278 [2]), but unfortunately it was also never adopted. [1] https://www.open-std.org/jtc1/sc22/wg14/www/docs/n853.htm https://www.open-std.org/jtc1/sc22/wg14/www/docs/n853.htm [2] https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2278.pdf https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2278.pdf
  - Kranar 4y ago
    You are now mixing correct and conforming programs. Neither the C or C++ Standard mention anything involving correct programs. C uses the term conforming program and C++ uses the term well-formed program. In C a conforming program is any program that satisfies any single conforming implementation, even if said implementation includes extensions or non-portable constructs. A strictly conforming program is a program that satisfies every conforming implementation, which implies that said program does not produce an output that depends on undefined, unspecified, or implementation defined behavior. In C++ a well-formed program is any program that satisfies the syntax rules, diagnosable semantic rules and the one-definition rule.