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frontends/ast.cc: special-case zero width strings as "\0"

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* Fixes #4696
This commit is contained in:
George Rennie 2024-11-01 16:57:10 +01:00
parent b2d78589e2
commit dbfca1bdff
1 changed files with 17 additions and 8 deletions
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25
frontends/ast/ast.cc
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@ -877,16 +877,25 @@ AstNode *AstNode::mkconst_str(const std::vector<RTLIL::State> &v)
// create an AST node for a constant (using a string as value)
AstNode *AstNode::mkconst_str(const std::string &str)
{
std::vector<RTLIL::State> data;
data.reserve(str.size() * 8);
for (size_t i = 0; i < str.size(); i++) {
unsigned char ch = str[str.size() - i - 1];
for (int j = 0; j < 8; j++) {
data.push_back((ch & 1) ? State::S1 : State::S0);
ch = ch >> 1;
AstNode *node;
// LRM 1364-2005 5.2.3.3 The empty string literal ("") shall be considered
// equivalent to the ASCII NUL ("\0")
if (str.empty()) {
node = AstNode::mkconst_int(0, false, 8);
} else {
std::vector<RTLIL::State> data;
data.reserve(str.size() * 8);
for (size_t i = 0; i < str.size(); i++) {
unsigned char ch = str[str.size() - i - 1];
for (int j = 0; j < 8; j++) {
data.push_back((ch & 1) ? State::S1 : State::S0);
ch = ch >> 1;
}
}
node = AstNode::mkconst_bits(data, false);
}
AstNode *node = AstNode::mkconst_bits(data, false);
node->is_string = true;
node->str = str;
return node;