Category Archives: isoc99 scanf

Isoc99 scanf

By | 14.07.2020

Red Hat Associate. Red Hat Customer. Browse Requests Reports Product Dashboard. Page Help! This site requires JavaScript to be enabled to function correctly, please enable it. Comment 1 yawei Li UTC. Comment 3 yawei Li UTC.

undefined reference to `__isoc99_sscanf'

Note You need to log in before you can comment on or make changes to this bug. Keywords :. Bug Fix. Attachments Terms of Use Add an attachment proposed patch, testcase, etc.

This is rooted in the difference in stdio. Version-Release number of selected component if applicable : Red Hat 6. Steps to Reproduce: 1. Actual results: Expected results: Additional info: Comment 1 yawei Li UTC would you please confirm you are raising bug for bugzilla? Maybe you want to raise bug for RH6.

I don't know enough about the differences between bugzilla and Red Hat. Please focus on the stdio. That define does not exist on RHEL 5.

Arvind, what we need from you is a reproducible testcase so that we can investigate why the linker was unable to resolve this symbol. Comment 9 Jeff Law UTC Arvind, per comment 7we need a testcase which shows this problem so that we can analyze and take appropriate action.

Without a testcase there really isn't anything we can do at this time. I have compiled this test on RH 5. As I mentioned, there is a change in the header files which causes this issue. See the undefined scanf function name difference show in the output of nm command. I need a testcase showing that link failure.

If I take the testcase from your most recent command and add a main function, it links fine. It appears that the lack of static link on the recent RH 6. If you like you can close the case. However, it will be great if such issues are widely documented. Thanks for the follow up.

At this point I don't see a bug in the behaviour of any of the tools. Could you please show me the actual failing testcase, compilation line, nm symbols, link line, output from failed link, output from rpm -qa. Comment 15 Arvind Amin UTC I am including the original link error which happened almost a year ago.

We used the work around and moved on. I no longer have the original app environment available since it was a customer project.

As I said, it may be a documentation need. If you're going to use the compat-glibc libraries for linking you must use the compat-glibc headers when you compile your code.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. I was studying various compiler option in GCC and observing changes when I made changes in the standard to be used.

What is the difference between these two forms of scanf?

isoc99 scanf

Any link where I can see their source would be highly appreciated. The reason is strict following of c99 disallow some existing GNU extension conversion specifiers. Learn more. Asked 6 years, 11 months ago. Active 4 years, 8 months ago. Viewed 11k times. Active Oldest Votes. In glibc 2.

This modifier was introduced in C Sign up or log in Sign up using Google. Sign up using Facebook.

isoc99 scanf

Sign up using Email and Password. Post as a guest Name. Email Required, but never shown.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. Reverse Engineering Stack Exchange is a question and answer site for researchers and developers who explore the principles of a system through analysis of its structure, function, and operation.

It only takes a minute to sign up. I have recently started getting into assembly for the purpose of reverse engineering. I started small with understanding basic datatypes, but I want to move on to more complex datatypes and functions. I am trying to understand what is happening in both methods requestMaxPow and computePowers. The assembly below is for the requestMaxPow method, which is the hardest for me to understand.

Specifically I don't understand what "gs" means at 0xc5, and I have no idea what is going on between lines 0xce - 0x The assembly for the computePowers method is much easier to understand. I include it just in case it has relevance to my main question. Edit 1 After looking at the code for a while longer I realized the xor is happening on eax to "0" it out, does that happen so that a return value can be stored into eax? The code between c5 and ce sets up the stack canaryand e7 to f3 checks it.

Your xor eax, eax isn't neccesary per se you don't need to zero registers before storing something into themit's just that the compiler wants to make the canary value unknown as soon as possible. Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. How does scanf interact with my code in assembly Ask Question.

Asked 4 years, 7 months ago. Active 4 years, 7 months ago. Viewed 5k times. Loligans Loligans 13 1 1 silver badge 4 4 bronze badges. GuntramBlohm Thank you for that! That makes complete sense. I looked up the Stack Canary on google and saw that it is a defense mechanism in Linux that helps make stack buffer overflows more difficult. At address 0xd7 why is a seemingly random address 0xb0 being pushed onto the stack?

I changed my comment to an answer to have space to explain more. Active Oldest Votes. In C, function arguments are pushed from behind, i. This ensures the first argument is always at the same position, which is important for varargs functions like printf and scanf.

sscanf() function in C

Since 2 arguments are passed, which needs 8 bytes, ommiting the first sub esp,0x8 and replacing the add esp,0x10 with add esp, 0x8 would be more straightforward. The reason gcc spends these extra bytes is probably that it wants the stack pointer aligned to a multiple of 16 bytes, which speeds up certain things.This is an optional starting asterisk, which indicates that the data is to be read from the stream but ignored, i.

Specifies a size different from int in the case of d, i and nunsigned int in the case of o, u and x or float in the case of e, f and g for the data pointed by the corresponding additional argument: h : short int for d, i and nor unsigned short int for o, u and x l : long int for d, i and nor unsigned long int for o, u and xor double for e, f and g L : long double for e, f and g. A character specifying the type of data to be read and how it is expected to be read.

See next table. For each format specifier in the format string that retrieves data, an additional argument should be specified. If you want to store the result of a sscanf operation on a regular variable you should precede its identifier with the reference operator, i. On success, the function returns the number of variables filled. In the case of an input failure before any data could be successfully read, EOF is returned. C library function - sscanf Advertisements.

isoc99 scanf

Previous Page. Next Page. Live Demo. Previous Page Print Page. Single character: Reads the next character. If a width different from 1 is specified, the function reads width characters and stores them in the successive locations of the array passed as argument. No null character is appended at the end. Two examples of valid entries are String of characters. This will read subsequent characters until a whitespace is found whitespace characters are considered to be blank, newline and tab.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. Basically, it returns the total number of inputs you just typed into the computer. Learn more.

isoc99 scanf

Asked 6 years, 1 month ago. Active 9 months ago. Viewed 12k times. LC1 V eax. L leave ret. GNU-stack,"", progbits. AbhishekSaha AbhishekSaha 2 2 gold badges 8 8 silver badges 20 20 bronze badges. This is bit code, so EAX before the call is not meaningful. Which will always be 0 for scanf because you pass pointers, not values, unless the caller has undefined behaviour by passing it some FP values.

Active Oldest Votes. I think this helps: man scanf: These functions return the number of input items successfully matched and assigned, which can be fewer than provided for, or even zero in the event of an early matching failure. Jonathan Davies Jonathan Davies 1. The code in the question uses a format string of. And sscanf returns intso technically it's not safe to assume it's correctly zero-extended into RAX; the upper 4 bytes of RAX could hold garbage.

But this is bit code so that point is moot anyway. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog.Review your favorite Linux distribution. Welcome to LinuxQuestions. You are currently viewing LQ as a guest. By joining our community you will have the ability to post topics, receive our newsletter, use the advanced search, subscribe to threads and access many other special features.

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Click Here to receive this Complete Guide absolutely free. Please help me find a solution. Regards, Harish. Originally Posted by harishisnow. Originally Posted by Nominal Animal. You have glibc version prior to 2. You can use command Code:. Hi guys New one here. I am also having the same problem installing Nagios Plugins.

It will resolve the issue.

Using Scanf() To Read Int, Float, Char and String Data Type: C Programming

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Already on GitHub? Sign in to your account. It looks like clang-upc2c is converting calls to certain stdio scanf-family functions to some internal name.

These names are now declared anywhere, resulting in implcit decl warnings from non-clang backends. Some examples from the many test failures appear below. Thanks for looking into this. So, no that I see where the defines come from, I wonder why is the back-end preprocess different?

So, probably this is something that upcc needs to deal with by ensuring consistent preprocess environments for the translation and compilation stages. So, I'll take assignment on this one. I also checked the 3. Is this some new configuration that we haven't tested before? This is not a new configuration. The problem appears to go back to when the host "tesla" was rebuilt and I don't know why I've not taken note of it before. I am certain now of the difference between initial and final pre-process.

However, in the final pre-process of the. There is not an obvious way to disable it without including our own wrapper. Skip to content.

Dismiss Join GitHub today GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Sign up. New issue. Jump to bottom. Copy link Quote reply. This comment has been minimized. Sign in to view. PHHargrove self-assigned this Feb 10, Member Author. Nenad, Thanks for looking into this. Hargrove wrote: Nenad, Thanks for looking into this. Nenad, This is not a new configuration.

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