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POWhy is passing a string literal into a char* argument only sometimes a compiler error?
 

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  1. POWhy is passing a string literal into a char* argument only sometimes a compiler error?
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    <p>I'm working in a C, and C++ program. We used to be compiling without the make-strings-writable option. But that was getting a bunch of warnings, so I turned it off.</p> <p>Then I got a whole bunch of errors of the form "Cannot convert const char* to char* in argmuent 3 of function foo". So, I went through and made a whole lot of changes to fix those. </p> <p>However, today, the program CRASHED because the literal "" was getting passed into a function that was expecting a char*, and was setting the 0th character to 0. It wasn't doing anything bad, just trying to edit a constant, and crashing. </p> <p>My question is, why wasn't that a compiler error? </p> <p>In case it matters, this was on a mac compiled with gcc-4.0.</p> <p>EDIT: added code:</p> <pre><code>char * host = FindArgDefault("EMailLinkHost", ""); stripCRLF(linkHost, '\n'); </code></pre> <p>where:</p> <pre><code>char *FindArgDefault(char *argName, char *defVal) {// simplified char * val = defVal; return(val); } </code></pre> <p>and</p> <pre><code>void stripCRLF(char *str, char delim) { char *p, *q; for (p = q = str; *p; ++p) { if (*p == 0xd || *p == 0xa) { if (p[1] == (*p ^ 7)) ++p; if (delim == -1) *p = delim; } *q++ = *p; } *q = 0; // DIES HERE } </code></pre> <p>This compiled and ran until it tried to set *q to 0...</p> <p>EDIT 2:</p> <p>Most people seem to be missing the point of my question. I know why char foo[] = "bar" works. I know why char * foo = "bar"; doesn't work. </p> <p>My question is mostly with respect to passing parameters. One thing that occures to me is "Is it possible that this is a C vs C++ issue?" because I have some .c files and some .cpp files, and it's quite possible that C allows it, but C++ doesn't... or vice versa...</p>
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    1. USBrian Postow
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    1. CODo you have example code we can look at?
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    2. COThe rule of thumb is that you should treat string literals always as const char *. Treating them as char * exposes you to these kind of problems.
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      1. USMatteo Italia
    3. CO@matteo: of course. My question is why did the compiler catch SOME of them, but not all...
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      1. USBrian Postow
 

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