When these invalid sym files were used during subsequent compiles, certain type pointers (for what should be const-qualified struct or union types) could be left uninitialized, or possibly initialized pointing to different types. This could result in spurious errors or potentially in other problems.
This relates to unions or structs that are "filled" with zeros because the initializer does not include explicit terms for them, and that contain bit-fields or (for unions) do not start with the longest member.
The following program is an example that was miscompiled:
#include <stdio.h>
struct BF {
int i:3;
int j:4;
};
union U {
int i;
long l;
};
struct Outer1 {
int n;
struct BF bf[7];
union U u[5];
};
struct Outer2 {
long p;
struct Outer1 o1;
long q;
};
int main(void) {
static struct Outer2 s = {1,{0},212};
printf("%li %li\n", s.p, s.q);
}
This fixes case 1 (dealing with run-time initialization of structures containing bit-fields) and case 2 (dealing with initialization of structs where initializer values are not provided for all elements) from issue #59. It also fixes cases that could result in invalid initialization of unions if their first element was not the longest, as in the following example:
#include <stdio.h>
union U {
int i;
long l;
};
int main(void) {
union U a[5] = {1,2,3,4};
printf("a[0].i=%i, a[1].i=%i, a[2].i=%i, a[3].i=%i, a[4].i=%i\n",
a[0].i, a[1].i, a[2].i, a[3].i, a[4].i);
}
This was an alias for double, but it's non-standard and undocumented. Apparently it existed in some other pre-standard compilers, but it's not in any version of standard C, and I can't find any evidence of it being used. Considering the possibility for confusion, I think it's best to remove it.
This allows debuggers to stop on the declaration lines, and also provides trace-back information for them if that feature is enabled.
Currently, this applies only to declarations that occur after the first statement in the block. As such, it doesn't change the handling of traditional pre-C99-style declarations at the beginning of a block.
An extra, fourth byte was being generated for the bitfield(s). This would cause all subsequent members of the struct and any enclosing object not to be initialized at the proper locations, which would generally corrupt their values.
The following program illustrates the issue:
#include <stdio.h>
struct X {
int a:9;
int b:9;
int c;
} x = {123,234,12345};
int main(void) {
printf("x.a = %i, x.b = %i, x.b = %i\n", x.a, x.b, x.c);
}
The initialized bytes for the bitfield(s) could wind up improperly being placed after those for the non-bitfield, generally corrupting both values.
The following program illustrates the problem:
#include <stdio.h>
struct X {
int a:9;
int b;
} x = {42,123};
int main(void) {
printf("x.a = %i, x.b = %i\n", x.a, x.b);
}
Note that this code currently permits discarding the const qualifier via such an initialization. That should give a diagnostic, but currently it doesn't in this or various other cases.
The following code (derived from a csmith-generated test case) illustrates the problem:
struct S0 {
const long f4;
};
const struct S0 g_149;
const long *g_311 = &g_149.f4;
This would lead to errors in programs like the following:
int main(void) {
typedef int x;
x: ;
}
Even before support for mixed statements and declarations was introduced, this error could happen if the labeled statement was the first statement after the declarations in a block (as in the above example). Adding that support also allowed this error to happen with later statements in a block. The C4.2.4.1.CC test case was affected by this.
Under these rules, if, switch, for, while, and do statements each have their own block scopes separate from the enclosing scope, and their substatements also have their own block scopes.
This patch always applies the C99 scope rules, but a flag can be changed to disable them or make them conditional on a configuration setting.
In the case of structs or unions, an error is now produced. This addresses one of the problems mentioned in issue #53.
In the case of arrays, tentative definitions like "int i[];" are now permitted at file scope. If not completed by a subsequent definition, this winds up producing an array with one element, initialized to 0. See the discussion and example in C99/C11 section 6.9.2 (or C90 section 6.7.2 and example in TC1).
If there are no varargs calls (and nothing else that saves stack positions), then space doesn't need to be allocated for the saved stack position. This can also lead to more efficient prolog/epilog code for small functions.
For example, the following is now allowed:
typedef void v;
void foo(v) {}
This appears to be permitted under at least C99 and C11 (the C89 wording is less clear), and is accepted by other modern compilers.
These are enabled when bit 15 is set in the #pragma debug directive.
Support is still needed to ensure these work properly with pre-compiled headers.
This patch is from Kelvin Sherlock.
Previously, several optimizations would be disabled for the rest of the translation unit whenever the keyword 'volatile' appeared. Now, if 'volatile' is used within a function, it only reduces optimization for that function, since whatever was declared as 'volatile' will be out of scope after the function is over. Uses of 'volatile' outside functions still behave as before.
This problem could cause "duplicate symbol" and "undeclared identifier" errors, for example in the following program:
typedef int f1( void );
void bar( void ) {
int i;
f1 *foo;
int baz;
i = 10;
}
int foo;
long baz;
This should give C99-compatible behavior, as far as it goes. The functions aren't actually inlined, but that's just a quality-of-implementation issue. No C standard requires actual inlining.
Non-static inline functions are still not supported. The C99 semantics for them are more complicated, and they're less widely used, so they're a lower priority for now.
The "inline" function specifier can currently only come after the "static" storage class specifier. This relates to a broader issue where not all legal orderings of declaration specifiers are supported.
Since "inline" was already treated as a keyword in ORCA/C, this shouldn't create any extra compatibility issues for C89 code.
ORCA/C previously allowed struct/union members to be declared with incomplete type. Because of this, it allowed C99-style flexible array members to be declared, albeit by accident rather than by design. In some basic testing, these seem to work correctly, except that they could be initialized and that would give rise to odd behavior.
I have restricted it to allowing flexible array members only in the cases allowed by C99/C11, and otherwise disallowing members with incomplete type. I have also prohibited initializing flexible array members.
Also, generate better code for zero-initializing small arrays.
The problem was that the code would call the library routine ~ZERO with a size of 1, but it only works properly with a size of 2 or more. While adding a check here, I also changed it to not call ~ZERO for other small arrays (<=10 bytes), since it is generally more efficient to just initialize them directly.
The initializations in the following are examples that could trigger the problem:
int main(void)
{
struct { int i; char s[1]; } foo = {1, 0};
char arr[2][1] = {2};
}
This may be someone trying to use a C11-style anonymous struct/union, which should be flagged as an error until and unless those are supported. Otherwise, it probably just indicates that the programmer is confused. In any case, an error should be flagged for it.
C89 restricts bit fields to (signed) int and unsigned int only, although later standards note that additional types may be supported. ORCA/C supports the other integer types as an extension.
This fixes the compco01.c test case.
This patch should also permit the union initialization code to handle unions containing bit fields, but for the time being they are still prohibited by code elsewhere in the compiler.
The case label values are converted to the promoted type of the expression being switched on, as if by a cast. In practice, this means discarding the high bits of a 32-bit value to produce a 16-bit one.
Code requiring this is dubious and would be a good candidate for a warning or a lint error, but it's allowed under the C standards.
The following code demonstrates the issue:
#include <stdio.h>
int main(void)
{
int i = 0x1234;
switch (i) {
case 0xABCD1234:
puts("good");
break;
default:
puts("bad");
}
}
