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[ruby/json] Fix: generate_json_float to reserve enough memory for large negative floats.

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Fix: https://github.com/ruby/json/issues/807

Since https://github.com/ruby/json/pull/800, `fpconv_dtoa` can actually
generate up to 28 chars.

https://github.com/ruby/json/commit/d73ae93d3c
This commit is contained in:
Jean Boussier 2025-05-23 09:28:56 +02:00 committed by Hiroshi SHIBATA
parent aa00a2d07b
commit f171a263f7
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GPG Key ID: F9CF13417264FAC2
3 changed files with 11 additions and 7 deletions
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5
ext/json/generator/generator.c
View File

@ -1406,10 +1406,9 @@ static void generate_json_float(FBuffer *buffer, struct generate_json_data *data
} }
/* This implementation writes directly into the buffer. We reserve /* This implementation writes directly into the buffer. We reserve
* the 24 characters that fpconv_dtoa states as its maximum, plus * the 28 characters that fpconv_dtoa states as its maximum.
* 2 more characters for the potential ".0" suffix.
*/ */
fbuffer_inc_capa(buffer, 26); fbuffer_inc_capa(buffer, 28);
char* d = buffer->ptr + buffer->len; char* d = buffer->ptr + buffer->len;
int len = fpconv_dtoa(value, d); int len = fpconv_dtoa(value, d);

8
ext/json/vendor/fpconv.c vendored
View File

@ -432,8 +432,8 @@ static int filter_special(double fp, char* dest)
* *
* Input: * Input:
* fp -> the double to convert, dest -> destination buffer. * fp -> the double to convert, dest -> destination buffer.
* The generated string will never be longer than 24 characters. * The generated string will never be longer than 28 characters.
* Make sure to pass a pointer to at least 24 bytes of memory. * Make sure to pass a pointer to at least 28 bytes of memory.
* The emitted string will not be null terminated. * The emitted string will not be null terminated.
* *
* Output: * Output:
@ -443,7 +443,7 @@ static int filter_special(double fp, char* dest)
* *
* void print(double d) * void print(double d)
* { * {
* char buf[24 + 1] // plus null terminator * char buf[28 + 1] // plus null terminator
* int str_len = fpconv_dtoa(d, buf); * int str_len = fpconv_dtoa(d, buf);
* *
* buf[str_len] = '\0'; * buf[str_len] = '\0';
@ -451,7 +451,7 @@ static int filter_special(double fp, char* dest)
* } * }
* *
*/ */
static int fpconv_dtoa(double d, char dest[24]) static int fpconv_dtoa(double d, char dest[28])
{ {
char digits[18]; char digits[18];

5
test/json/json_generator_test.rb
View File

@ -795,6 +795,11 @@ class JSONGeneratorTest < Test::Unit::TestCase
expecteds << "1746861937.7842371" expecteds << "1746861937.7842371"
end end
if RUBY_ENGINE == "ruby"
values << -2.2471348024634545e-08 << -2.2471348024634545e-09 << -2.2471348024634545e-10
expecteds << "-0.000000022471348024634545" << "-0.0000000022471348024634545" << "-2.2471348024634546e-10"
end
values.zip(expecteds).each do |value, expected| values.zip(expecteds).each do |value, expected|
assert_equal expected, value.to_json assert_equal expected, value.to_json
end end