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py/parse: Fix macro evaluation by avoiding empty __VA_ARGS__.
Empty __VA_ARGS__ are not allowed in the C preprocessor so adjust the rule arg offset calculation to not use them. Also, some compilers (eg MSVC) require an extra layer of macro expansion.
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Lines changed: 17 additions & 10 deletions

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‎py/parse.c‎

Lines changed: 17 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -131,53 +131,60 @@ STATIC const uint16_t rule_arg_combined_table[] = {
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#undef opt_rule
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};
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134-
// Macro to create a list of N-1 identifiers where N is the number of variable arguments to the macro
134+
// Macro to create a list of N identifiers where N is the number of variable arguments to the macro
135+
#define RULE_EXPAND(x) x
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#define RULE_PADDING(rule, ...) RULE_PADDING2(rule, __VA_ARGS__, RULE_PADDING_IDS(rule))
136-
#define RULE_PADDING2(rule, ...) RULE_PADDING3(rule, __VA_ARGS__)
137-
#define RULE_PADDING3(rule, _1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _13, ...) __VA_ARGS__
137+
#define RULE_PADDING2(rule, ...) RULE_EXPAND(RULE_PADDING3(rule, __VA_ARGS__))
138+
#define RULE_PADDING3(rule, _1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, ...) __VA_ARGS__
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#define RULE_PADDING_IDS(r) PAD12_##r, PAD11_##r, PAD10_##r, PAD9_##r, PAD8_##r, PAD7_##r, PAD6_##r, PAD5_##r, PAD4_##r, PAD3_##r, PAD2_##r, PAD1_##r,
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140-
// Use an enum to create constants that specify where in rule_arg_combined_table a given rule starts
141+
// Use an enum to create constants specifying how much room a rule takes in rule_arg_combined_table
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enum {
142-
#define DEF_RULE(rule, comp, kind, ...) RULE_ARG_OFFSET_##rule, RULE_PADDING(rule, __VA_ARGS__)
143+
#define DEF_RULE(rule, comp, kind, ...) RULE_PADDING(rule, __VA_ARGS__)
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#define DEF_RULE_NC(rule, kind, ...)
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#include "py/grammar.h"
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#undef DEF_RULE
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#undef DEF_RULE_NC
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#define DEF_RULE(rule, comp, kind, ...)
148-
#define DEF_RULE_NC(rule, kind, ...) RULE_ARG_OFFSET_##rule, RULE_PADDING(rule, __VA_ARGS__)
149+
#define DEF_RULE_NC(rule, kind, ...) RULE_PADDING(rule, __VA_ARGS__)
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#include "py/grammar.h"
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#undef DEF_RULE
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#undef DEF_RULE_NC
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};
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155+
// Macro to compute the start of a rule in rule_arg_combined_table
156+
#define RULE_ARG_OFFSET(rule, ...) RULE_ARG_OFFSET2(rule, __VA_ARGS__, RULE_ARG_OFFSET_IDS(rule))
157+
#define RULE_ARG_OFFSET2(rule, ...) RULE_EXPAND(RULE_ARG_OFFSET3(rule, __VA_ARGS__))
158+
#define RULE_ARG_OFFSET3(rule, _1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _13, ...) _13
159+
#define RULE_ARG_OFFSET_IDS(r) PAD12_##r, PAD11_##r, PAD10_##r, PAD9_##r, PAD8_##r, PAD7_##r, PAD6_##r, PAD5_##r, PAD4_##r, PAD3_##r, PAD2_##r, PAD1_##r, PAD0_##r,
160+
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// Use the above enum values to create a table of offsets for each rule's arg
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// data, which indexes rule_arg_combined_table. The offsets require 9 bits of
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// storage but only the lower 8 bits are stored here. The 9th bit is computed
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// in get_rule_arg using the FIRST_RULE_WITH_OFFSET_ABOVE_255 constant.
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STATIC const uint8_t rule_arg_offset_table[] = {
159-
#define DEF_RULE(rule, comp, kind, ...) RULE_ARG_OFFSET_##rule & 0xff,
166+
#define DEF_RULE(rule, comp, kind, ...) RULE_ARG_OFFSET(rule, __VA_ARGS__) & 0xff,
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#define DEF_RULE_NC(rule, kind, ...)
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#include "py/grammar.h"
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#undef DEF_RULE
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#undef DEF_RULE_NC
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0, // RULE_const_object
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#define DEF_RULE(rule, comp, kind, ...)
166-
#define DEF_RULE_NC(rule, kind, ...) RULE_ARG_OFFSET_##rule & 0xff,
173+
#define DEF_RULE_NC(rule, kind, ...) RULE_ARG_OFFSET(rule, __VA_ARGS__) & 0xff,
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#include "py/grammar.h"
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#undef DEF_RULE
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#undef DEF_RULE_NC
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};
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// Define a constant that's used to determine the 9th bit of the values in rule_arg_offset_table
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static const size_t FIRST_RULE_WITH_OFFSET_ABOVE_255 =
174-
#define DEF_RULE(rule, comp, kind, ...) RULE_ARG_OFFSET_##rule >= 0x100 ? RULE_##rule :
181+
#define DEF_RULE(rule, comp, kind, ...) RULE_ARG_OFFSET(rule, __VA_ARGS__) >= 0x100 ? RULE_##rule :
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#define DEF_RULE_NC(rule, kind, ...)
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#include "py/grammar.h"
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#undef DEF_RULE
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#undef DEF_RULE_NC
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#define DEF_RULE(rule, comp, kind, ...)
180-
#define DEF_RULE_NC(rule, kind, ...) RULE_ARG_OFFSET_##rule >= 0x100 ? RULE_##rule :
187+
#define DEF_RULE_NC(rule, kind, ...) RULE_ARG_OFFSET(rule, __VA_ARGS__) >= 0x100 ? RULE_##rule :
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#include "py/grammar.h"
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#undef DEF_RULE
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#undef DEF_RULE_NC

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