Here's an example that shows the issues (derived from a csmith-generated test case):
struct S {
unsigned f;
};
void f1(struct S p) {
printf("%u\n", p.f);
}
int main(void) {
const struct S l = {123};
struct S s;
f1(l);
s = l;
printf("%u\n", s.f);
}
Such subexpressions are not of the right form to work with the existing code, because they do not generate a value for use in the enclosing expression. For now, the code has been changed to simply not remove the subexpression in these cases. Alternative code could be written to make it work, but that might be more trouble than it's worth.
Here's an example that shows the problem (derived from a csmith-generated test case):
#pragma optimize 32+1 /* also had a problem with just 32 */
int main(void) {
int x, y=10; /* also had problems if x was global */
do {
x=42, y-=1;
} while (y);
return x+y;
}
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.
commit 4265329097538640e9e21202f1b141bcd42a44f3
Author: Kelvin Sherlock <ksherlock@gmail.com>
Date: Fri Mar 23 21:45:32 2018 -0400
indent to match standard indent.
commit 783518fbeb01d2df43ef2083d3341004c05e4e2e
Author: Kelvin Sherlock <ksherlock@gmail.com>
Date: Fri Mar 23 20:21:15 2018 -0400
clean up the typenames
commit 29b627ecf5ca9b8a143761f85a1807a6ca35ddd9
Author: Kelvin Sherlock <ksherlock@gmail.com>
Date: Fri Mar 23 20:18:04 2018 -0400
enable feature_hh, warn about %n with non-int modifier.
commit fc4ac8129e3772c4eda36658e344ec475938369c
Author: Kelvin Sherlock <ksherlock@gmail.com>
Date: Fri Mar 23 15:13:47 2018 -0400
warn thar %lc, %ls, etc are unsupported.
commit 7e6b433ba0552f7e52f0f034d398e9195c764326
Author: Kelvin Sherlock <ksherlock@gmail.com>
Date: Fri Mar 23 13:36:25 2018 -0400
warn about hh/ll modifier (if not supported)
commit 1943c9979d0013f9f38045ec04a962fbf0269f31
Author: Kelvin Sherlock <ksherlock@gmail.com>
Date: Fri Mar 23 11:42:41 2018 -0400
use error facilities for format errors.
commit 7811168f56dca1387055574ba8d32638da2fad96
Author: Kelvin Sherlock <ksherlock@gmail.com>
Date: Thu Mar 22 15:34:21 2018 -0400
add feature flags to disable c99 enhancements until orca lib is updated.
commit c2149cc5953155cfc3c3b4d0483cd25fb946b055
Author: Kelvin Sherlock <ksherlock@gmail.com>
Date: Thu Mar 22 08:59:10 2018 -0400
Add printf/scanf format checking [WIP]
This parses out the xprintf / xscanf format string and compares it with the function arguments.
enabled via #pragma lint 16.
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).
Memory for them is still allocated from the global pool, to ensure they remain available for as long as the function prototype that references them.
This addresses one of the problems mentioned in issue #53.
In order to work right, this needs either GNO's ORCALib (which already included isblank()) or a copy of ORCA's ORCALib with the corresponding patch applied.
Previously, when a struct type first appeared in a symbol table nested within another struct type, subsequent references to that type would use the wrong offset and be corrupted. This occurred because the symbol table length had not yet been updated to reflect the size of the entry for the outer structure at the time the inner one was processed.
Fixes#54.
It had been changed to reflect changes in the ORCALib code that added a second putback buffer element, but those changes were problematic and have been reverted for now. (It's also not clear if ORCALib binaries with the larger putback buffer were ever distributed--at the least, they aren't on Opus ][ or in any of the ORCA/C 2.2.0 beta releases.)
This allows the code to be displayed properly on GitHub and in modern text editors, which typically do not support the irregularly-spaced tab stops used for ORCA/M code. It also avoids any possibility of problems building the code if the SysTabs file is missing or has been customized with non-standard tab stops.
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.
Previously, the stack repair code always generated code to save and restore a register, but this can be omitted except in cases where a 32-bit value or pointer is returned.
Previously, when stack repair code was generated, it always included instructions to save and restore a previously-saved stack position, but this was only actually used for function calls nested within the arguments to other function calls using stack repair code. Now that code is only generated in cases where it is needed, and the stack repair code for other calls is simplified to omit it.
This optimization affects all (non-nested) function calls when not using optimize bit 3, and varargs function calls when not using optimize bit 6.
This could occur due to the new native-code peephole optimizations for stz instructions, which can collapse consecutive identical ones down to one instruction. This is OK most of the time, but not when dealing with volatile variables, so disable it in that case.
The following test case shows the issue (look at the generated code):
#pragma optimize -1
volatile int a;
int main(void) {
a = 0;
a = 0;
}
This could happen in native-code peephole optimization if two stz instructions targeting different global/static locations occurred consecutively.
This was a regression introduced by commit a3170ea7.
The following program demonstrates the problem:
#pragma optimize 1+2+8+64
int i,j=1;
int main (void) {
i = 0;
j = 0;
return j; /* should return 0 */
}
These mainly related to situations where the optimization of multiple natural loops (including those created by continue statements) could interact to generate invalid results. Invalid optimizations could also be performed in certain other cases where there were multiple goto statements targeting a single label and at least one of them formed a loop.
These issues are addressed by appropriately adjusting the control flow and updating various data structures after each loop is processed during loop invariant removal.
This fixes#18 (compca18.c).
This should implement the C standard rules about making macro name tokens ineligible for replacement, except that it does not currently handle cases of nested replacements (such as a cycle of mutually-referential macros).
This fixes#12. There are still a couple other bugs with macro expansion in obscure cases, but I'll consider them separate issues.
The macro was slightly broken in that its 'buf' argument might be evaluated twice. This could be a problem if it was, e.g., a call to an allocation function.
This is needed to ensure correct behavior in cases where the macro is bypassed to access the library function, e.g. by enclosing the function name in parentheses or by taking its address.
These cases should now always work when using an expression of type unsigned as the index. They will work in some cases but not others when using an int as the index: making those cases work consistently would require more extensive changes and/or a speed hit, so I haven't done it for now.
Note that this now uses an "unsigned multiply" operation for all 16-bit index computations. This should actually work even when the index is a negative signed value, because it will wind up producing (the low-order 16 bits of) the right answer. The signed multiply, on the other hand, generally does not produce the low-order 16 bits of the right answer in cases where it overflows.
The following program is an example that was miscompiled (both with and without optimization):
int c[20000] = {3};
int main(void) {
int *p;
unsigned i = 17000;
p = c + 17000u;
return *(p-i); /* should return 3 */
}
This could occur with computations where multiple variables were added to a pointer.
The following program is an example that was miscompiled:
#pragma optimize 1
#pragma memorymodel 1
char c[80000];
int main(void) {
unsigned i = 30000, j = 40000;
c[70000] = 3;
return *(c+i+j); /* should return 3 */
}
This introduces a function to check whether the index portion of a pc_ixa intermediate code operation (used for array indexing) may be negative. This is also used when generating code for the large memory model, which can allow slightly more efficient code to be generated in some cases.
This fixes#45.
This type information is currently used when generating code for the large memory model, but not for the short memory model (which is a bug in itself, causing issue such as #45).
Because the correct type information was not being provided, the code generator could incorrectly use signed index computations when a 16-bit unsigned index value was used in large-memory-model code. The following program is an example that was being miscompiled:
#pragma optimize 1
#pragma memorymodel 1
char c[0xFFFF];
int main(void) {
unsigned i = 0xABCD;
c[0xABCD] = 3;
return c[i]; /* should return 3 */
}
This optimization could apply when indexing into an array whose elements are a power-of-2 size using a 16-bit index value. It is now only used when addressing arrays on the stack (which are necessarily smaller than 64k).
The following program demonstrates the problem:
#pragma optimize 1
#pragma memorymodel 1
long c[40000];
int main(void) {
int i = 30000;
c[30000] = 3;
return c[i]; /* should return 3 */
}
