This is related to: https://bugzilla.redhat.com/show_bug.cgi?id=841057 As noted there: When we locate an SDT marker, stap takes different paths depending on the presence of $vars in the handler. Without any $var, we just build the probe directly, and life is good. With a $var, we decide we need debuginfo, and so that goes down the query_addr path. Now, if there's anything wrong with the debuginfo, then we end up throwing up entirely with "semantic error: no match". An unreachable $var is a problem, sure, but we should use the right error. And this also means that @defined() can't work around this issue. It doesn't even have to be corrupt debuginfo, as rhbz841057. Even our sdt_asm test binary can show this, when you don't have DWARF in part of a file. First, with no DWARF at all: > $ gcc ../testsuite/systemtap.base/sdt_asm.S -o sdt_asm.x > $ ./run-stap -e 'probe process("./sdt_asm.x").mark("*") { println($foo) }' -p2 > WARNING: cannot find module /home/jistone/systemtap/build/sdt_asm.x debuginfo: No DWARF information found > semantic error: while resolving probe point: identifier 'process' at <input>:1:7 > source: probe process("./sdt_asm.x").mark("*") { println($foo) } > ^ > > semantic error: no match > Pass 2: analysis failed. Try again with another '--vp 01' option. With some DWARF added (but nothing meaningful near asm probes): > $ gcc ../testsuite/systemtap.base/sdt_asm.S -o sdt_asm.x -g > $ ./run-stap -e 'probe process("./sdt_asm.x").mark("*") { println($foo) }' -p2 > semantic error: while resolving probe point: identifier 'process' at <input>:1:7 > source: probe process("./sdt_asm.x").mark("*") { println($foo) } > ^ > > semantic error: no match > Pass 2: analysis failed. Try again with another '--vp 01' option. And just to sanity check that the probe points do exist: > $ ./run-stap -e 'probe process("./sdt_asm.x").mark("*") { println(1) }' -p2 > # probes > process("/home/jistone/systemtap/build/sdt_asm.x").statement(0x4004ab) /* pc=.absolute+0x4ab */ /* <- process("./sdt_asm.x").mark("memory") = process("./sdt_asm.x").statement(0x4004ab) <- process("./sdt_asm.x").mark("*") */ > process("/home/jistone/systemtap/build/sdt_asm.x").statement(0x4004b1) /* pc=.absolute+0x4b1 */ /* <- process("./sdt_asm.x").mark("a") = process("./sdt_asm.x").statement(0x4004b1) <- process("./sdt_asm.x").mark("*") */ [...] We ought to fall back on this direct method when the query_addr path fails, and then the $foo can fail later (if it even survives optimization).
(In reply to comment #0) > We ought to fall back on this direct method when the query_addr path fails, and > then the $foo can fail later (if it even survives optimization). commit 73d53dd2213ce54a72db9b3bd029eb1f39760656 With this, we now get: > $ gcc ../testsuite/systemtap.base/sdt_asm.S -o sdt_asm.x > $ ./run-stap -e 'probe process("./sdt_asm.x").mark("*") { println($foo) }' -p2 > WARNING: cannot find module /home/jistone/systemtap/build/sdt_asm.x debuginfo: No DWARF information found > semantic error: target-symbol requires debuginfo: identifier '$foo' at <input>:1:50 > source: probe process("./sdt_asm.x").mark("*") { println($foo) } > ^ > > Pass 2: analysis failed. Try again with another '--vp 01' option. > $ gcc ../testsuite/systemtap.base/sdt_asm.S -o sdt_asm.x -g > $ ./run-stap -e 'probe process("./sdt_asm.x").mark("*") { println($foo) }' -p2 > semantic error: target-symbol requires debuginfo: identifier '$foo' at <input>:1:50 > source: probe process("./sdt_asm.x").mark("*") { println($foo) } > ^ > > Pass 2: analysis failed. Try again with another '--vp 01' option. > $ ./run-stap -e 'probe process("./sdt_asm.x").mark("*") { println(@defined($foo)) }' -p2 > # probes > process("/home/jistone/systemtap/build/sdt_asm.x").statement(0x4004ab) /* pc=.absolute+0x4ab */ /* <- process("./sdt_asm.x").mark("memory") = process("./sdt_asm.x").statement(0x4004ab) <- process("./sdt_asm.x").mark("*") */ > process("/home/jistone/systemtap/build/sdt_asm.x").statement(0x4004b1) /* pc=.absolute+0x4b1 */ /* <- process("./sdt_asm.x").mark("a") = process("./sdt_asm.x").statement(0x4004b1) <- process("./sdt_asm.x").mark("*") */ I'm not entirely thrilled with how the new error gets chained though, when full debuginfo is present: > $ ./run-stap -e 'probe process("./stap").mark("*") { println($foo) }' -p2 > semantic error: unable to find local 'foo' near pc 0x41140f in cleanup ../main.cxx ( (alternatives: $s $rc): identifier '$foo' at <input>:1:45 > source: probe process("./stap").mark("*") { println($foo) } > ^ > > semantic error: target-symbol requires debuginfo: identifier '$foo' at :1:45 > source: probe process("./stap").mark("*") { println($foo) } > ^ > > Pass 2: analysis failed. Try again with another '--vp 01' option. Ideas on how to improve that are welcome...
(In reply to comment #1) > I'm not entirely thrilled with how the new error gets chained though, when full > debuginfo is present: [...] Ideas on how to improve that are welcome... fche declared it Good Enough, so I'm closing this bug.