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This is a self-answered Q&A meant as a C string handling FAQ. It will ask several questions at once which isn't ideal, but they are all closely related and I'd rather not fragment the post in...
#3: Post edited
by
Karl Knechtel
·
2024-11-13T20:39:18Z (1 day ago)
improve formatting; copyedit for clarity
Common string handling pitfalls in C programming
_Preface: This is a self-answered Q&A meant as a C string handling FAQ. It will ask several questions at once which isn't ideal, but they are all closely related and I'd rather not fragment the post into several._---When reading C programming forums or code written by beginners, there is a number of frequently recurring bugs related to string handling. These are not only written by complete beginners, but as often by experienced programmers coming from a higher level language and picking up C.The common bugs originates from them assuming that C like most languages has a built-in string class which will handle all string handling and memory allocation for them. Here follows some frequently occurring bugs and their related questions:---- Bug 1) `char str = "hello";`.This will luckily not even compile if the compiler is configured correctly, see [What compiler options are recommended for beginners learning C?](https://software.codidact.com/posts/282565)**Question: Why doesn't this work? Does C have a string class?**---- Bug 2) `char str[5] = "hello";`.Compiles just fine, yet when printing this there will be garbage printed or other strange behavior. This bug is related to character arrays and missing null termination.**Question: What exactly does a string consist of in C?**---- Bug 3) `char* str; scanf("%s", str);`Compiles just fine, though if lucky there can be warnings. This bug is related to memory allocation.**Question: Who is responsible for allocating memory for the string?**---- Bug 4) `char* str = malloc(5+1); str = "hello";`Compiles just fine, though there are memory leaks.**Question: How can a string get assigned a new value?**---- Bug 5) `char str[5+1] = "hello";` ... `if(str == "hello")`.Compiles just fine but gives the wrong results.**Question: How do you properly compare strings?**
- <section class="notice">
- This is a self-answered Q&A meant as a C string handling FAQ. It will ask several questions at once which isn't ideal, but they are all closely related and I'd rather not fragment the post into several._
- </section>
- Code written by beginners to C, or found on C programming forums, frequently contains a few specific string handling bugs. Even experienced programmers coming from a higher level language and picking up C may make these mistakes.
- These bugs seem to result from expecting C to have a built-in string class (like most languages do) which would handle all string operations and memory allocation for them.
- Here are some frequently occurring bugs with corresponding questions:
- 1. `char str = "hello";`.
- This will luckily not even compile if the compiler is configured correctly, see [What compiler options are recommended for beginners learning C?](https://software.codidact.com/posts/282565)
- **Question: Why doesn't this work? Does C have a string class?**
- 1. `char str[5] = "hello";`.
- Compiles just fine, yet when printing this there will be garbage printed or other strange behavior. This bug is related to character arrays and missing null termination.
- **Question: What exactly does a string consist of in C?**
- 1. `char* str; scanf("%s", str);`
- Compiles just fine, though if lucky there can be warnings. This bug is related to memory allocation.
- **Question: Who is responsible for allocating memory for the string?**
- 1. `char* str = malloc(5+1); str = "hello";`
- Compiles just fine, though there are memory leaks.
- **Question: How can a string get assigned a new value?**
- 1. `char str[5+1] = "hello";` ... `if(str == "hello")`.
- Compiles just fine but gives the wrong results.
- **Question: How do you properly compare strings?**
#2: Post edited
by
Lundin
·
2024-11-13T13:40:56Z (1 day ago)
_Preface: This is a self-answered Q&A meant as a C string handling FAQ. It will ask several question at once which isn't ideal, but they are all closely related and I'd rather not fragment the post into several._- ---
- When reading C programming forums or code written by beginners, there is a number of frequently recurring bugs related to string handling. These are not only written by complete beginners, but as often by experienced programmers coming from a higher level language and picking up C.
- The common bugs originates from them assuming that C like most languages has a built-in string class which will handle all string handling and memory allocation for them. Here follows some frequently occurring bugs and their related questions:
- ---
- - Bug 1) `char str = "hello";`.
- This will luckily not even compile if the compiler is configured correctly, see [What compiler options are recommended for beginners learning C?](https://software.codidact.com/posts/282565)
- **Question: Why doesn't this work? Does C have a string class?**
- ---
- - Bug 2) `char str[5] = "hello";`.
- Compiles just fine, yet when printing this there will be garbage printed or other strange behavior. This bug is related to character arrays and missing null termination.
- **Question: What exactly does a string consist of in C?**
- ---
- - Bug 3) `char* str; scanf("%s", str);`
- Compiles just fine, though if lucky there can be warnings. This bug is related to memory allocation.
- **Question: Who is responsible for allocating memory for the string?**
- ---
- - Bug 4) `char* str = malloc(5+1); str = "hello";`
- Compiles just fine, though there are memory leaks.
- **Question: How can a string get assigned a new value?**
- ---
- - Bug 5) `char str[5+1] = "hello";` ... `if(str == "hello")`.
- Compiles just fine but gives the wrong results.
- **Question: How do you properly compare strings?**
- _Preface: This is a self-answered Q&A meant as a C string handling FAQ. It will ask several questions at once which isn't ideal, but they are all closely related and I'd rather not fragment the post into several._
- ---
- When reading C programming forums or code written by beginners, there is a number of frequently recurring bugs related to string handling. These are not only written by complete beginners, but as often by experienced programmers coming from a higher level language and picking up C.
- The common bugs originates from them assuming that C like most languages has a built-in string class which will handle all string handling and memory allocation for them. Here follows some frequently occurring bugs and their related questions:
- ---
- - Bug 1) `char str = "hello";`.
- This will luckily not even compile if the compiler is configured correctly, see [What compiler options are recommended for beginners learning C?](https://software.codidact.com/posts/282565)
- **Question: Why doesn't this work? Does C have a string class?**
- ---
- - Bug 2) `char str[5] = "hello";`.
- Compiles just fine, yet when printing this there will be garbage printed or other strange behavior. This bug is related to character arrays and missing null termination.
- **Question: What exactly does a string consist of in C?**
- ---
- - Bug 3) `char* str; scanf("%s", str);`
- Compiles just fine, though if lucky there can be warnings. This bug is related to memory allocation.
- **Question: Who is responsible for allocating memory for the string?**
- ---
- - Bug 4) `char* str = malloc(5+1); str = "hello";`
- Compiles just fine, though there are memory leaks.
- **Question: How can a string get assigned a new value?**
- ---
- - Bug 5) `char str[5+1] = "hello";` ... `if(str == "hello")`.
- Compiles just fine but gives the wrong results.
- **Question: How do you properly compare strings?**
#1: Initial revision
by
Lundin
·
2021-11-12T11:09:09Z (about 3 years ago)
Common string handling pitfalls in C programming
_Preface: This is a self-answered Q&A meant as a C string handling FAQ. It will ask several question at once which isn't ideal, but they are all closely related and I'd rather not fragment the post into several._
---
When reading C programming forums or code written by beginners, there is a number of frequently recurring bugs related to string handling. These are not only written by complete beginners, but as often by experienced programmers coming from a higher level language and picking up C.
The common bugs originates from them assuming that C like most languages has a built-in string class which will handle all string handling and memory allocation for them. Here follows some frequently occurring bugs and their related questions:
---
- Bug 1) `char str = "hello";`.
This will luckily not even compile if the compiler is configured correctly, see [What compiler options are recommended for beginners learning C?](https://software.codidact.com/posts/282565)
**Question: Why doesn't this work? Does C have a string class?**
---
- Bug 2) `char str[5] = "hello";`.
Compiles just fine, yet when printing this there will be garbage printed or other strange behavior. This bug is related to character arrays and missing null termination.
**Question: What exactly does a string consist of in C?**
---
- Bug 3) `char* str; scanf("%s", str);`
Compiles just fine, though if lucky there can be warnings. This bug is related to memory allocation.
**Question: Who is responsible for allocating memory for the string?**
---
- Bug 4) `char* str = malloc(5+1); str = "hello";`
Compiles just fine, though there are memory leaks.
**Question: How can a string get assigned a new value?**
---
- Bug 5) `char str[5+1] = "hello";` ... `if(str == "hello")`.
Compiles just fine but gives the wrong results.
**Question: How do you properly compare strings?**