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Support shader preprocessor concatenation symbol #74737

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merged 1 commit into from
Aug 8, 2023
Merged

Support shader preprocessor concatenation symbol #74737

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65 changes: 55 additions & 10 deletions servers/rendering/shader_preprocessor.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -420,11 +420,11 @@ void ShaderPreprocessor::process_define(Tokenizer *p_tokenizer) {
return;
}

Vector<String> args;
if (p_tokenizer->peek() == '(') {
// Macro has arguments.
p_tokenizer->get_token();

Vector<String> args;
while (true) {
String name = p_tokenizer->get_identifier();
if (name.is_empty()) {
Expand All @@ -442,17 +442,24 @@ void ShaderPreprocessor::process_define(Tokenizer *p_tokenizer) {
return;
}
}
}

Define *define = memnew(Define);
String body = tokens_to_string(p_tokenizer->advance('\n')).strip_edges();
if (body.begins_with("##")) {
set_error(RTR("'##' must not appear at beginning of macro expansion."), line);
return;
}
if (body.ends_with("##")) {
set_error(RTR("'##' must not appear at end of macro expansion."), line);
return;
}

Define *define = memnew(Define);
if (!args.is_empty()) {
define->arguments = args;
define->body = tokens_to_string(p_tokenizer->advance('\n')).strip_edges();
state->defines[label] = define;
} else {
// Simple substitution macro.
Define *define = memnew(Define);
define->body = tokens_to_string(p_tokenizer->advance('\n')).strip_edges();
state->defines[label] = define;
}
define->body = body;
state->defines[label] = define;
}

void ShaderPreprocessor::process_elif(Tokenizer *p_tokenizer) {
Expand Down Expand Up @@ -1074,9 +1081,13 @@ bool ShaderPreprocessor::expand_macros_once(const String &p_line, int p_line_num
}
}

concatenate_macro_body(body);

result = result.substr(0, index) + " " + body + " " + result.substr(args_end + 1, result.length());
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I removed the padding " " because they made unit testing much more complicated. Have not found any case where this caused problems.

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Should be fine, like I mentioned in RocketChat adding those spaces might have been there "just in case".

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@JohanAR JohanAR Mar 14, 2023 •
edited
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I found one case where it changes the behaviour:

#define MOD +
float a MOD= 1.0;

Previously this would've been expanded to invalid code, while now it works. I did some tests with a C++ compiler and it doesn't work there.

Should I revert this line and update the tests to require the surrounding spaces? I think it would be difficult to relax the test to allow them without adding a full blown glsl parser/tokenizer.

On the other hand, this is probably an edge case, and I would say that (with my change) it works like I would expect it to.

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Was about to revert this padding change, but then I realised that the example above would not be affected since the padding was only done for macros with arguments.

E.g. before my PR the following defines:

#define A -10
#define B(x) -x
int n = 1-A;
int m = 1-B(3);

Would be expanded to:

int n = 1--10;
int m = 1- -3 ;

I.e. the behaviour changes depending on if you have args or not, and leading to one case where the code becomes invalid.

Kind of leaning towards adding the padding for argument-less macros too now, even if it'll make my unit tests uglier.

} else {
result = result.substr(0, index) + body + result.substr(index + key.length(), result.length() - (index + key.length()));
concatenate_macro_body(body);

result = result.substr(0, index) + " " + body + " " + result.substr(index + key.length(), result.length() - (index + key.length()));
}

r_expanded = result;
Expand Down Expand Up @@ -1115,6 +1126,40 @@ bool ShaderPreprocessor::find_match(const String &p_string, const String &p_valu
return false;
}

void ShaderPreprocessor::concatenate_macro_body(String &r_body) {
int index_start = r_body.find("##");
while (index_start > -1) {
int index_end = index_start + 2; // First character after ##.
// The macro was checked during creation so this should never happen.
ERR_FAIL_INDEX(index_end, r_body.size());

// If there more than two # in a row, then it's not a concatenation.
bool is_concat = true;
while (index_end <= r_body.length() && r_body[index_end] == '#') {
index_end++;
is_concat = false;
}
if (!is_concat) {
index_start = r_body.find("##", index_end);
continue;
}

// Skip whitespace after ##.
while (index_end < r_body.length() && is_char_space(r_body[index_end])) {
index_end++;
}

// Skip whitespace before ##.
while (index_start >= 1 && is_char_space(r_body[index_start - 1])) {
index_start--;
}

r_body = r_body.substr(0, index_start) + r_body.substr(index_end, r_body.length() - index_end);

index_start = r_body.find("##", index_start);
}
}

String ShaderPreprocessor::next_directive(Tokenizer *p_tokenizer, const Vector<String> &p_directives) {
const int line = p_tokenizer->get_line();
int nesting = 0;
Expand Down
1 change: 1 addition & 0 deletions servers/rendering/shader_preprocessor.h
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Original file line number Diff line number Diff line change
Expand Up @@ -205,6 +205,7 @@ class ShaderPreprocessor {
Error expand_macros(const String &p_string, int p_line, String &r_result);
bool expand_macros_once(const String &p_line, int p_line_number, const RBMap<String, Define *>::Element *p_define_pair, String &r_expanded);
bool find_match(const String &p_string, const String &p_value, int &r_index, int &r_index_start);
void concatenate_macro_body(String &r_body);

String next_directive(Tokenizer *p_tokenizer, const Vector<String> &p_directives);
void add_to_output(const String &p_str);
Expand Down
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