STM32 + GCC v8 + Qt Creator + Qbs : crash in __libc_init_array - gcc

Question

After upgrading my host PC to a newer Linux version, I can't run my project anymore. I just want to program a copy of a working electronic board : hardware and code have been validated before.
More accurately, the code crashes in the startup script at _libc_init_array and jump either to BusFault_Handler() or HardFault_Handler().
I have read a lot on the forum, and it seems is related to linking to the wrong libc flavor (Thumb vs. ARM).
Tools :
code generation : STM32CubeMX
compiler : GNU GCC version 8.2.1 (8-2018-q4-major)
IDE : Qt Creator
build system : Qbs (Qt's tool)
The MCU is a STM32L476RG, Cortex-M4, ARM v7e-m, with FPU. In GNU GCC installation folder, share/doc/gcc-arm-none-eabi/readme.txt tells me what flags I need :
|------------|--------------------------------------------|--------------|
| Cortex-M4 | -mthumb -mcpu=cortex-m4 -mfloat-abi=softfp | thumb |
| (Soft FP) | -mfpu=fpv4-sp-d16 | /v7e-m+fp |
| |--------------------------------------------| /softfp |
| | -mthumb -march=armv7e-m -mfloat-abi=softfp | |
| | -mfpu=fpv4-sp-d16 | |
|------------|--------------------------------------------|--------------|
| Cortex-M4 | -mthumb -mcpu=cortex-m4 -mfloat-abi=hard | thumb |
| (Hard FP) | -mfpu=fpv4-sp-d16 | /v7e-m+fp |
| |--------------------------------------------| /hard |
| | -mthumb -march=armv7e-m -mfloat-abi=hard | |
| | -mfpu=fpv4-sp-d16 | |
|------------|--------------------------------------------|--------------|
Only -mfloat-abi=softfp works, not -mfloat-abi=hard, but GCC documentation suggests the result is the same ; only calling conventions differ.
Here is my Qbs file :
import qbs
CppApplication {
consoleApplication: true
property string family: "STM32L4xx"
property string linkerScript: "STM32L476RGTx_FLASH.ld"
cpp.positionIndependentCode: false // make sure option -fPIC is not passed to GCC
cpp.defines: [
"USE_HAL_DRIVER",
"STM32L476xx",
"__weak=__attribute__((weak))",
"__packed=__attribute__((__packed__))"
]
cpp.commonCompilerFlags: [
"-fno-common",
"-specs=nosys.specs",
"-specs=nano.specs",
"-march=armv7e-m",
"-mcpu=cortex-m4",
"-mthumb-interwork", // support ARM and Thumb instruction sets
"-mthumb",
"-mfloat-abi=softfp",
"-mfpu=fpv4-sp-d16",
"-mtune=cortex-m4", // tune performance of code for this processor
// "-std=c99",
"-ffunction-sections",
"-fdata-sections",
// "-Os",
"-O0",
"-g3",
"-Wall",
"-c", // don't run the linker
// "-v" // print a lot of details (too much ?)
]
cpp.linkerFlags: [
"-T"+path+"/"+linkerScript,
"--gc-sections", // fixes "undefined reference to _exit" error
"-Map="+buildDirectory+"/memory.map", // file created at the end of the link step
"-static",
"--verbose", // displays library search
// "-lgcc",
// "-lg",
// "-lm"
]
cpp.includePaths: [
"Inc",
"Drivers/CMSIS/Include",
"Drivers/CMSIS/Device/ST/"+family+"/Include",
"Drivers/STM32L4xx_HAL_Driver/Inc",
"Middlewares/ST/STM32_USB_Device_Library/Class/CDC/Inc",
"Middlewares/ST/STM32_USB_Device_Library/Core/Inc/"
]
files: [
"Inc/*.h",
linkerScript,
"Src/*.c",
"Drivers/CMSIS/Device/ST/"+family+"/Include/*.h",
"Drivers/CMSIS/Device/ST/"+family+"/Source/Templates/gcc/*.s",
"Drivers/CMSIS/Device/ST/"+family+"/Source/Templates/*.c",
"Drivers/CMSIS/Include/*.h",
"Drivers/"+family+"_HAL_Driver/Inc/*.h",
"Drivers/"+family+"_HAL_Driver/Src/*.c",
"Middlewares/ST/STM32_USB_Device_Library/Class/CDC/Src/*.c",
"Middlewares/ST/STM32_USB_Device_Library/Core/Src/*.c"
]
Properties {
condition: qbs.buildVariant === "debug"
cpp.defines: outer.concat(["DEBUG=1"])
}
Group { // Properties for the produced executable
fileTagsFilter: product.type
qbs.install: true
}
}
The linker --verbose option lets it print the full path of the libraries it links to. And it always resolves to arm-none-eabi/lib/libc.a. But I would have expected arm-none-eabi/lib/thumb/v7e-m+fp/softfp/libc.a instead.
I also tried the linker option -nostdlib in conjunction with the -L flag , but it has no effect. It compiles even when I omit -L, but according to GCC man page, it shouldn't.
So, I am pretty stuck here. That 5 minute work is turning into days...

Answer 1

The problem was that the newer version of Qbs I got (v1.12.1) is smart enough to prepend "-Wl," to all options under cpp.linkerFlags... The solution is to set those flags needed to compile AND link in a cpp.driverFlags section.
Should it be helpful to anyone, here is my working (to date ;-) ) Qbs file.
import qbs
CppApplication {
consoleApplication: true
property string family: "STM32L4xx"
property string linkerScript: "STM32L476RGTx_FLASH.ld"
cpp.positionIndependentCode: false // make sure option -fPIC is not passed to GCC
// Make sure to call the linker through GCC driver :
cpp.linkerMode: "manual" // default : "automatic"
cpp.linkerName: "gcc" // this string is appended to "<full_path_to_toolchain>/arm-none-eabi-"
// Define some symbols (GCC -D flag)
cpp.defines: [
"USE_HAL_DRIVER",
"STM32L476xx",
"__weak=__attribute__((weak))",
"__packed=__attribute__((__packed__))"
]
// Options for compilation AND linking.
cpp.driverFlags: [
// CPU
"-mcpu=cortex-m4",
"-mthumb",
"-mfpu=fpv4-sp-d16",
"-mfloat-abi=hard",
"-specs=nano.specs", // use smaller libc
]
// Compiler flags for all langages (C, C++).
cpp.commonCompilerFlags: [
// Optimizations
//"-Os",
//"-O0",
"-Og",
"-Wall",
"-fdata-sections",
"-ffunction-sections",
// For debug
"-g",
"-gdwarf-2",
"-c", // don't run the linker
//"-v" // print a whole lot of details
]
// Linker flag only i.e. understood by LD !!!
// Qbs will prepend all these flags with "-Wl," so that GCC transfers them to LD.
// Other options required for linking should be set in the driverFlags section.
cpp.linkerFlags: [
"-T"+path+"/"+linkerScript,
"-static",
"--verbose", // displays library search
"-lc",
"-lm",
"-lnosys",
"-Map="+buildDirectory+"/memory.map", // file created at the end of the link step
"--cref", // map file formatting
"--gc-sections", // enables garbage collection for unused sections
]
// Include directories.
cpp.includePaths: [
"Inc",
"Drivers/CMSIS/Include",
"Drivers/CMSIS/Device/ST/"+family+"/Include",
"Drivers/STM32L4xx_HAL_Driver/Inc",
"Middlewares/ST/STM32_USB_Device_Library/Class/CDC/Inc",
"Middlewares/ST/STM32_USB_Device_Library/Core/Inc/"
]
// Source files.
files: [
"Inc/*.h",
linkerScript,
"Src/*.c",
"Drivers/CMSIS/Device/ST/"+family+"/Include/*.h",
"startup/*.s",
"Drivers/CMSIS/Device/ST/"+family+"/Source/Templates/*.c",
"Drivers/CMSIS/Include/*.h",
"Drivers/"+family+"_HAL_Driver/Inc/*.h",
"Drivers/"+family+"_HAL_Driver/Src/*.c",
"Middlewares/ST/STM32_USB_Device_Library/Class/CDC/Src/*.c",
"Middlewares/ST/STM32_USB_Device_Library/Core/Src/*.c"
]
Properties {
condition: qbs.buildVariant === "debug"
cpp.defines: outer.concat(["DEBUG=1"])
}
Group { // Properties for the produced executable
fileTagsFilter: product.type
qbs.install: true
}
}