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Revert "Forbid 3-byte struct pass/return by value, document struct value pass/return"

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Bob Andrews 2023-05-03 14:24:13 +02:00 committed by GitHub
parent f3c0f7c6ce
commit 6ffc4004d7
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3 changed files with 5 additions and 147 deletions
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7
doc/cc65.sgml
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@ -741,7 +741,7 @@ Here is a description of all the command line options:
<tag><tt/return-type/</tag>
Warn about no return statement in function returning non-void.
<tag><tt/struct-param/</tag>
Warn when passing structs by value. (Disabled by default.)
Warn when passing structs by value.
<tag><tt/unknown-pragma/</tag>
Warn about #pragmas that aren't recognized by cc65.
<tag><tt/unreachable-code/</tag>
@ -806,8 +806,9 @@ and the one defined by the ISO standard:
<item> The datatypes "float" and "double" are not available.
<p>
<item> C Functions may pass and return structs (or unions) by value, but only
of 1, 2 or 4 byte sizes.
<item> C Functions may not return structs (or unions), and structs may not
be passed as parameters by value. However, struct assignment *is*
possible.
<p>
<item> Most of the C library is available with only the fastcall calling
convention (<ref id="extension-fastcall" name="see below">). It means

1
src/cc65/datatype.c
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@ -803,6 +803,7 @@ const Type* GetStructReplacementType (const Type* SType)
switch (SizeOf (SType)) {
case 1: NewType = type_uchar; break;
case 2: NewType = type_uint; break;
case 3: /* FALLTHROUGH */
case 4: NewType = type_ulong; break;
default: NewType = SType; break;
}

144
test/val/struct-by-value.c
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@ -1,144 +0,0 @@
/* Test of passing and returning structs by value.
Structs of 1, 2 and 4 bytes are supported.
Note that structs of 3 bytes are disabled, see:
https://github.com/cc65/cc65/issues/2022
*/
int fail = 0;
struct s1 { char a; };
struct s2 { char a, b; };
struct s3 { char a, b, c; };
struct s4 { char a, b, c, d; };
const struct s1 c1 = { 1 };
const struct s2 c2 = { 2, 3 };
const struct s3 c3 = { 4, 5, 6 };
const struct s4 c4 = { 7, 8, 9, 10 };
struct s1 return1() { return c1; }
struct s2 return2() { return c2; }
/*struct s3 return3() { return c3; }*/
struct s4 return4() { return c4; }
int compare1(struct s1 a, struct s1 b)
{
if (a.a != b.a) return 1;
return 0;
}
int compare2(struct s2 a, struct s2 b)
{
if (a.a != b.a) return 1;
if (a.b != b.b) return 1;
return 0;
}
/*int compare3(struct s3 a, struct s3 b)
{
if (a.a != b.a) return 1;
if (a.b != b.b) return 1;
if (a.c != b.c) return 1;
return 0;
}*/
int compare4(struct s4 a, struct s4 b)
{
if (a.a != b.a) return 1;
if (a.b != b.b) return 1;
if (a.c != b.c) return 1;
if (a.d != b.d) return 1;
return 0;
}
int pass1(struct s1 p1)
{
struct s1 a1;
a1 = p1;
if (a1.a != c1.a) return 1;
return 0;
}
int pass2(struct s2 p2)
{
struct s2 a2;
a2 = p2;
if (a2.a != c2.a) return 1;
if (a2.b != c2.b) return 1;
return 0;
}
/*int pass3(struct s3 p3)
{
struct s3 a3;
a3 = p3;
if (a3.a != c3.a) return 1;
if (a3.b != c3.b) return 1;
if (a3.c != c3.c) return 1;
return 0;
}*/
int pass4(struct s4 p4)
{
struct s4 a4;
a4 = p4;
if (a4.a != c4.a) return 1;
if (a4.b != c4.b) return 1;
if (a4.c != c4.c) return 1;
if (a4.d != c4.d) return 1;
return 0;
}
void reset(char* gg)
{
char i;
for (i=0;i<5;++i) gg[i] = 128+i;
}
int test(char* gg, char start)
{
char i;
for (i=start;i<5;++i)
if (gg[i] != 128+i) return 1;
return 0;
}
int main()
{
/* Used to check #2022 bug condition of extra bytes being overwritten. */
union
{
char gg[5];
struct s1 g1;
struct s2 g2;
struct s3 g3;
struct s4 g4;
} guard;
reset(guard.gg);
guard.g1 = return1();
fail += compare1(guard.g1,c1);
fail += test(guard.gg,1);
reset(guard.gg);
guard.g2 = return2();
fail += compare2(guard.g2,c2);
fail += test(guard.gg,2);
/*reset(guard.gg);
guard.g3 = return3();
fail += compare3(guard.g3,c3);
fail += test(guard.gg,3);*/
reset(guard.gg);
guard.g4 = return4();
fail += compare4(guard.g4,c4);
fail += test(guard.gg,4);
fail += pass1(c1);
fail += pass2(c2);
/*fail += pass3(c3);*/
fail += pass4(c4);
return fail;
}