Unmatched format specifier causes crashes but not compile errors

[maskit]

I realized a scary behavior change on compile. Code like below that has unmatched format specifiers used to cause compile errors, but we no longer see it on master because of some changes around Diag.

diff --git a/proxy/http2/Http2ClientSession.cc b/proxy/http2/Http2ClientSession.cc
index 434b4a3c4..4ada20fca 100644
--- a/proxy/http2/Http2ClientSession.cc
+++ b/proxy/http2/Http2ClientSession.cc
@@ -208,7 +208,7 @@ Http2ClientSession::new_connection(NetVConnection *new_vc, MIOBuffer *iobuf, IOB
     Debug("ssl_early_data", "read_from_early_data = %" PRId64, this->read_from_early_data);
   }
 
-  Http2SsnDebug("session born, netvc %p", this->_vc);
+  Http2SsnDebug("session born, netvc %p %s", this->_vc);
 
   this->_vc->set_tcp_congestion_control(CLIENT_SIDE);
 

On 9.1.x branch, the code above does not compile.

Http2ClientSession.cc:211:42: error: more '%' conversions than data arguments [-Werror,-Wformat-insufficient-args]
  Http2SsnDebug("session born, netvc %p %s", this->_vc);
                                        ~^

But on master, I don't see the compile error, and ATS crashes when I run it.

* thread #5, name = '[ET_NET 3]', stop reason = EXC_BAD_ACCESS (code=1, address=0x41b58ab3)
  * frame #0: 0x0000000104604df0 libclang_rt.asan_osx_dynamic.dylib`__sanitizer::internal_strlen(char const*) + 16
    frame #1: 0x00000001045ca7c5 libclang_rt.asan_osx_dynamic.dylib`printf_common(void*, char const*, __va_list_tag*) + 2069
    frame #2: 0x00000001045caa17 libclang_rt.asan_osx_dynamic.dylib`wrap_vfprintf + 103
    frame #3: 0x00000001039f0372 libtscore.10.dylib`Diags::print_va(this=0x0000612000000ac0, debug_tag="http2_cs", diags_level=DL_Debug, loc=0x000000010195ce80, format_string="[%lld] session born, netvc %p %s", ap=0x00000001092fe320) const at Diags.cc:273:7

The change above is something I made up to demonstrate the error, but a real error on master is already hidden by the behavior change. I see this compile error below on 9.1.x but not on master.

HttpSessionManager.cc:150:79: error: format specifies type 'long long' but the argument has type 'size_t' (aka 'unsigned long') [-Werror,-Wformat]
    Debug("http_ss", "Search for host name only not IP.  Pool size %" PRId64, m_fqdn_pool.count());
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~
../../include/tscore/Diags.h:330:39: note: expanded from macro 'Debug'
      diags->log(tag, DL_Debug, &loc, __VA_ARGS__);    \
                                      ^~~~~~~~~~~
1 error generated.

[bryancall]

@Firebush Can you please take a look at this?

[ywkaras]

I think these functions:

trafficserver/include/tscore/LogMessage.h

Lines 63 to 74 in 5c39528

	void diag(const char *tag, SourceLocation const &loc, const char *fmt, ...);
	void debug(const char *tag, SourceLocation const &loc, const char *fmt, ...);
	void status(SourceLocation const &loc, const char *fmt, ...);
	void note(SourceLocation const &loc, const char *fmt, ...);
	void warning(SourceLocation const &loc, const char *fmt, ...);
	void error(SourceLocation const &loc, const char *fmt, ...);
	void fatal(SourceLocation const &loc, const char *fmt, ...);
	void alert(SourceLocation const &loc, const char *fmt, ...);
	void emergency(SourceLocation const &loc, const char *fmt, ...);
	void message(DiagsLevel level, SourceLocation const &loc, const char *fmt, ...);
	void print(const char *tag, DiagsLevel level, SourceLocation const &loc, const char *fmt, ...);

Need an invocation of the TS_PRINTFLIKE macro in their declarations.

[bneradt]

Good catch @maskit .

Thank you for the observation, @ywkaras . That looks like it works. I've created a PR for this: #7829 .