@matheusbsbs / matheus-bagliano / commits / c69dfd24db

trace: add infrastructure to augment trace output with additional info

To be able to add a common prefix or suffix to all trace output (e.g. a timestamp or file:line of the caller), factor out common setup and cleanup tasks of the trace* functions. When adding a common prefix, it makes sense that the output of each trace call starts on a new line. Add '\n' in case the caller forgot. Note that this explicitly limits trace output to line-by-line, it is no longer possible to trace-print just part of a line. Until now, this was just an implicit assumption (trace-printing part of a line worked, but messed up the trace file if multiple threads or processes were involved). Thread-safety / inter-process-safety is also the reason why we need to do the prefixing and suffixing in memory rather than issuing multiple write() calls. Write_or_whine_pipe() / xwrite() is atomic unless the size exceeds MAX_IO_SIZE (8MB, see wrapper.c). In case of trace_strbuf, this costs an additional string copy (which should be irrelevant for performance in light of actual file IO). While we're at it, rename trace_strbuf's 'buf' argument, which suggests that the function is modifying the buffer. Trace_strbuf() currently is the only trace API that can print arbitrary binary data (without barfing on '%' or stopping at '\0'), so 'data' seems more appropriate. Signed-off-by: Karsten Blees <blees@dcon.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Karsten Blees committed Jul 12, 2014 at 02:02 UTC c69dfd24db21be54ec5a17bb3e07c81f4e96861a

2 files changed +34 -15

trace.c

+33 -14

@@ -85,17 +85,37 @@ void trace_disable(struct trace_key *key)

85 static const char err_msg[] = "Could not trace into fd given by "

86 "GIT_TRACE environment variable";

88 +static int prepare_trace_line(struct trace_key *key, struct strbuf *buf)

89 +{

90 + if (!trace_want(key))

91 + return 0;

92 +

93 + set_try_to_free_routine(NULL); /* is never reset */

94 +

95 + /* add line prefix here */

96 +

97 + return 1;

98 +}

99 +

100 +static void print_trace_line(struct trace_key *key, struct strbuf *buf)

101 +{

102 + /* append newline if missing */

103 + if (buf->len && buf->buf[buf->len - 1] != '\n')

104 + strbuf_addch(buf, '\n');

105 +

106 + write_or_whine_pipe(get_trace_fd(key), buf->buf, buf->len, err_msg);

107 + strbuf_release(buf);

108 +}

109 +

110 static void trace_vprintf(struct trace_key *key, const char *format, va_list ap)

111 {

112 struct strbuf buf = STRBUF_INIT;

113

92 - if (!trace_want(key))

114 + if (!prepare_trace_line(key, &buf))

115 return;

116

95 - set_try_to_free_routine(NULL); /* is never reset */

117 strbuf_vaddf(&buf, format, ap);

97 - trace_strbuf(key, &buf);

98 - strbuf_release(&buf);

118 + print_trace_line(key, &buf);

119 }

120

121 void trace_printf_key(struct trace_key *key, const char *format, ...)

@@ -114,32 +134,31 @@ void trace_printf(const char *format, ...)

134 va_end(ap);

135 }

136

117 -void trace_strbuf(struct trace_key *key, const struct strbuf *buf)

137 +void trace_strbuf(struct trace_key *key, const struct strbuf *data)

138 {

119 - int fd = get_trace_fd(key);

120 - if (!fd)

139 + struct strbuf buf = STRBUF_INIT;

140 +

141 + if (!prepare_trace_line(key, &buf))

142 return;

143

123 - write_or_whine_pipe(fd, buf->buf, buf->len, err_msg);

144 + strbuf_addbuf(&buf, data);

145 + print_trace_line(key, &buf);

146 }

147

148 void trace_argv_printf(const char **argv, const char *format, ...)

149 {

150 struct strbuf buf = STRBUF_INIT;

151 va_list ap;

130 - int fd = get_trace_fd(NULL);

131 - if (!fd)

152 +

153 + if (!prepare_trace_line(NULL, &buf))

154 return;

155

134 - set_try_to_free_routine(NULL); /* is never reset */

156 va_start(ap, format);

157 strbuf_vaddf(&buf, format, ap);

158 va_end(ap);

159

160 sq_quote_argv(&buf, argv, 0);

140 - strbuf_addch(&buf, '\n');

141 - write_or_whine_pipe(fd, buf.buf, buf.len, err_msg);

142 - strbuf_release(&buf);

161 + print_trace_line(NULL, &buf);

162 }

163

164 static const char *quote_crnl(const char *path)

trace.h

+1 -1

@@ -22,6 +22,6 @@ extern int trace_want(struct trace_key *key);

22 extern void trace_disable(struct trace_key *key);

23 __attribute__((format (printf, 2, 3)))

24 extern void trace_printf_key(struct trace_key *key, const char *format, ...);

25 -extern void trace_strbuf(struct trace_key *key, const struct strbuf *buf);

25 +extern void trace_strbuf(struct trace_key *key, const struct strbuf *data);

27 #endif /* TRACE_H */