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Add a DTrace probe for string capacity resizes #110

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Add a DTrace probe for string capacity resizes #110

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12 changes: 12 additions & 0 deletions probes.d
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Original file line number Diff line number Diff line change
Expand Up @@ -151,6 +151,18 @@ provider ruby {
*/
probe string__create(long length, const char *filename, int lineno);

/*
ruby:::string-capa-resize(from_capa, to_capa, filename, lineno);

This probe is fired when String capacity is changed

* `from_capa` the current capacity of the string (long)
* `to_capa` the new capacity of the string (long)
* `filename` the name of the file where the string is allocated (string)
* `lineno` the line number in the file where the string is allocated (int)
*/
probe string__capa__resize(long from_capa, long to_capa, const char *filename, int lineno);

/*
ruby:::symbol-create(str, filename, lineno);

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12 changes: 12 additions & 0 deletions string.c
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Expand Up @@ -132,6 +132,18 @@ VALUE rb_cSymbol;
RESIZE_CAPA_TERM(str,capacity,termlen);\
} while (0)
#define RESIZE_CAPA_TERM(str,capacity,termlen) do {\
if (UNLIKELY(RUBY_DTRACE_STRING_CAPA_RESIZE_ENABLED())) {\
int dtrace_line; \
const char *dtrace_file = rb_source_location_cstr(&dtrace_line); \
long prev_capa;\
if (STR_EMBED_P(str)) {\
prev_capa = RSTRING_EMBED_LEN_MAX + 1 - termlen;\
} else {\
prev_capa = RSTRING(str)->as.heap.aux.capa;\
}\
if (!dtrace_file) dtrace_file = ""; \
RUBY_DTRACE_STRING_CAPA_RESIZE(prev_capa, capacity, dtrace_file, dtrace_line);\
}\
if (STR_EMBED_P(str)) {\
if (!STR_EMBEDDABLE_P(capacity, termlen)) {\
char *const tmp = ALLOC_N(char, (size_t)(capacity) + (termlen));\
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