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POWhat could make GDB refuse to break?
 

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    <p>I'm at a loss here. I'm writing a compiler in C (for hobby), and compiling with GCC 4.6.1 on amd64 Linux 2.6.32, using GDB 7.3. Flags are "-Wall -Wextra -O0 -g", in addition to the usual -I and whatnot. I have a function whose purpose is to report a parse error, defined as follows:</p> <pre><code>void cerror_at (struct lex *lex, struct token *tok, const char *fmt, ...) </code></pre> <p>Other than being variadic, nothing weird. The problem is that GDB will NOT break at it. I've tried every way I can think of (breakpoint at the function, inside the function, before it's called, you name it), but as soon as my program is inside the function, I get messages like "warning: Error removing breakpoint 0" and GDB just lets the program finish. There's nothing wrong with it any more (I've since fixed the bug I was trying to find, and everything runs as it should), but I can't get into the function. Any ideas on what could cause this?</p> <p><strong>Edit:</strong> More information! GDB is setting the breakpoint at 0x403057. The function starts at 0x403025. Look at this part of the disassembly:</p> <pre><code>0x0000000000403053 &lt;+46&gt;: test %al,%al 0x0000000000403055 &lt;+48&gt;: je 0x403077 &lt;cerror_at+82&gt; </code></pre> <p>At this point, it skips ahead to 0x403077 (past the breakpoint). I've verified that placing the breakpoint at an address before the "je" works, as well as at an address at or after 0x403077, the target of the jump, but not in between (where GDB is trying to place it). Why would GDB place the breakpoint in the middle of the function? Even GDB tells me that the function's address is, in fact, 0x403025.</p>
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    1. COJust a couple thoughts that you've probably considered already: Is the code actually being executed, and is the breakpoint on an executable statement?
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    2. COYes, the code is definitely being executed; I can see the error message it prints out. The breakpoints outside the function are either right on the call itself, which is definitely executable, or on the function call before it that discovers the error condition. The breakpoint inside the function gets placed on an fprintf().
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    3. COMore info - I just tried getting into the function using 'si', one instruction at a time. It actually does go in, but the line numbers it reports jump around, it seems to have no clue what it's doing, and then it gives me the same "Error removing breakpoint" message at the end of the function.
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