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Diagnostics that are errors in --strict mode are downgraded to warnings, where possible. It is sometimes not possible for the compiler to downgrade a strict error, for example, where it cannot construct a legitimate program to recover.


When --strict_warnings is in force and a violation of the relevant ISO standard occurs, the compiler normally issues a warning message.

The severity of diagnostic messages can be controlled in the usual way.


In some cases, the compiler issues an error message instead of a warning when it detects something that is strictly illegal, and terminates the compilation. For example:

#ifdef $Super$
extern void $Super$$__aeabi_idiv0(void); /* intercept __aeabi_idiv0 */

Compiling this code with --strict_warnings generates an error if you do not use the --dollar option.


void foo(void)
    long long i; /* okay in nonstrict C90 */

Compiling this code with --strict_warnings generates a warning message.

Compilation continues, even though the expression long long is strictly illegal.